updates install instructions for debian (#675)

- Updated install instructions in allignment to: https://wiki.debian.org/DebianRepository/UseThirdParty

- Markdown cleanup

Signed-off-by: Toni Förster <toni.foerster@icloud.com>

Author: stonerl

README.md

@@ -43,7 +43,6 @@ sudo cp ../init/launchd/homebrew.mxcl.et.plist /Library/LaunchDaemons/homebrew.m
 sudo launchctl load -w /Library/LaunchDaemons/homebrew.mxcl.et.plist
 ```
 
-
 Alternatively, a package is available in MacPorts:
 
 ```
@@ -62,14 +61,14 @@ sudo apt-get install et
 
 Or see "Debian/Ubuntu" below to install and build from source (e.g., for ARM).
 
-
 ### Debian
 
-For debian, use our deb repo. For buster:
+For Debian, use our deb repo:
 
 ```
-echo "deb https://github.com/MisterTea/debian-et/raw/master/debian-source/ buster main" | sudo tee -a /etc/apt/sources.list.d/et.list
-curl -sSL https://github.com/MisterTea/debian-et/raw/master/et.gpg | sudo tee /etc/apt/trusted.gpg.d/et.gpg >/dev/null
+echo "deb [signed-by=/etc/apt/keyrings/et.gpg] https://mistertea.github.io/debian-et/debian-source/ $(grep VERSION_CODENAME /etc/os-release | cut -d= -f2) main" | sudo tee -a /etc/apt/sources.list.d/et.list
+sudo mkdir -m 0755 -p /etc/apt/keyrings # only if you're using Debian 11 or older
+curl -sSL https://github.com/MisterTea/debian-et/raw/master/et.gpg | sudo tee /etc/apt/keyrings/et.gpg >/dev/null
 sudo apt update
 sudo apt install et
 ```
@@ -86,6 +85,7 @@ sudo dnf install et
 ```
 
 ### FreeBSD
+
 On FreeBSD, use:
 
 ```
@@ -110,14 +110,14 @@ zypper in EternalTerminal
 
 Install dependencies:
 
-* Fedora (tested on 25):
+- Fedora (tested on 25):
 
   ```
   sudo dnf install boost-devel libsodium-devel protobuf-devel \
   	protobuf-compiler cmake gflags-devel libcurl-devel
   ```
 
-* Gentoo:
+- Gentoo:
 
   ```
   sudo emerge dev-libs/boost dev-libs/libsodium \
@@ -138,7 +138,7 @@ sudo make install
 
 ### Windows
 
-Eternal Terminal works under WSL (Windows Subsystem for Linux).  Follow the ubuntu instructions.
+Eternal Terminal works under WSL (Windows Subsystem for Linux). Follow the ubuntu instructions.
 
 ### Docker Image
 
@@ -148,7 +148,7 @@ See [docker/README.md](docker/)
 
 Verify that the client is installed correctly by looking for the `et` executable: `which et`.
 
-Verify that the server is installed correctly by checking the service status: `systemctl status et`.  On some operating systems, you may need to enable and start the service manually: `sudo systemctl enable --now et`.
+Verify that the server is installed correctly by checking the service status: `systemctl status et`. On some operating systems, you may need to enable and start the service manually: `sudo systemctl enable --now et`.
 
 You are ready to start using ET!
 
@@ -163,20 +163,25 @@ ET uses ssh for handshaking and encryption, so you must be able to ssh into the
 ET uses TCP, so you need an open port on your server. By default, it uses 2022.
 
 Once you have an open port, the syntax is similar to ssh. Username is default to the current username starting the et process, use `-u` or `user@` to specify a different if necessary.
+
 ```
 et hostname (etserver running on default port 2022, username is the same as current)
 et user@hostname:8000 (etserver running on port 8000, different user)
 ```
+
 You can specify a jumphost and the port et is running on jumphost using `--jumphost` and `--jport`. If no `--jport` is given, et will try to connect to default port 2022.
+
 ```
 et hostname -jumphost jump_hostname (etserver running on port 2022 on both hostname and jumphost)
 et hostname:8888 --jumphost jump_hostname --jport 9999
 ```
+
 Additional arguments that et accept are port forwarding pairs with option `-t "18000:8000, 18001-18003:8001-8003"`, a command to run immediately after the connection is setup through `-c`.
 
 Starting from the latest release, et supports parsing both user-specific and system-wide ssh config file.
 The config file is required when your sshd on server/jumphost is listening on a port which is not 22.
 Here is an example ssh config file showing how to setup when
+
 - there is a jumphost in the middle
 - sshd is listening on a port which is not 22
 - connecting to a different username other than current one.
@@ -212,7 +217,7 @@ cmake ../
 make -j$(nproc) && sudo make install
 ```
 
-To run an `et` server for testing, run `./etserver`.  To run an `et`
+To run an `et` server for testing, run `./etserver`. To run an `et`
 server daemon persistently across reboots:
 
 ```
@@ -249,10 +254,10 @@ sudo cp ../etc/et.cfg /etc/
 
 Once built, the binary only requires `libprotobuf-dev`.
 
-
 ### CentOS 7
 
 Install dependencies:
+
 ```
 sudo yum install epel-release
 sudo yum install cmake3 boost-devel libsodium-devel protobuf-devel \
@@ -261,12 +266,14 @@ sudo yum install cmake3 boost-devel libsodium-devel protobuf-devel \
 ```
 
 Install scl dependencies
+
 ```
 sudo yum install centos-release-scl
 sudo yum install devtoolset-11 devtoolset-11-libatomic-devel rh-git227
 ```
 
 Download and install from source ([see #238 for details](https://github.com/MisterTea/EternalTerminal/issues/238)):
+
 ```
 git clone --recurse-submodules --depth 1 https://github.com/MisterTea/EternalTerminal.git
 cd EternalTerminal
@@ -280,7 +287,7 @@ sudo cp ../etc/et.cfg /etc/
 
 Find the actual location of et:
 
-	which etserver
+    which etserver
 
 Correct the service file (see [#180](https://github.com/MisterTea/EternalTerminal/issues/180) for details).
 
@@ -290,7 +297,7 @@ sudo sed -ie "s|ExecStart=[^[:space:]]*[[:space:]]|ExecStart=$(which etserver) |
 
 Alternativelly, open the file /etc/systemd/system/et.service in an editor and correct the `ExectStart=...` line to point to the correct path of the `etserver` binary.
 
-	 ExecStart=/usr/local/bin/etserver --cfgfile=/etc/et.cfg
+     ExecStart=/usr/local/bin/etserver --cfgfile=/etc/et.cfg
 
 Reload systemd configs:
 
@@ -317,4 +324,3 @@ If you have any problems with installation or usage, please [file an issue on gi
 - Jason Gauci: https://github.com/MisterTea
 - Ailing Zhang: https://github.com/ailzhang
 - James Short: https://github.com/jshort
-