Move section on adding CPM higher in the Readme (#454)

Repositions the "Adding CPM" section higher in the Readme to increase incentive to try it out and make it easier to find for updating CPM in existing projects.

Author: TheLartians

README.md

@@ -45,6 +45,18 @@ target_link_libraries(main fmt::fmt nlohmann_json::nlohmann_json Catch2::Catch2W
 
 See the [examples directory](https://github.com/cpm-cmake/CPM.cmake/tree/master/examples) for complete examples with source code and check [below](#snippets) or in the [wiki](https://github.com/cpm-cmake/CPM.cmake/wiki/More-Snippets) for example snippets.
 
+## Adding CPM
+
+To add CPM to your current project, simply add the [latest release](https://github.com/cpm-cmake/CPM.cmake/releases/latest) of `CPM.cmake` or `get_cpm.cmake` to your project's `cmake` directory.
+The command below will perform this automatically.
+
+```bash
+mkdir -p cmake
+wget -O cmake/CPM.cmake https://github.com/cpm-cmake/CPM.cmake/releases/latest/download/get_cpm.cmake
+```
+
+You can also download CPM.cmake directly from your project's `CMakeLists.txt`. See the [wiki](https://github.com/cpm-cmake/CPM.cmake/wiki/Downloading-CPM.cmake-in-CMake) for more details.
+
 ## Usage
 
 After `CPM.cmake` has been [added](#adding-cpm) to your project, the function `CPMAddPackage` can be used to fetch and configure a dependency.
@@ -107,21 +119,9 @@ For using CPM.cmake projects with external package managers, such as conan or vc
 
 In rare cases, this behaviour may be desirable by default. The function `CPMFindPackage` will try to find a local dependency via CMake's `find_package` and fallback to `CPMAddPackage`, if the dependency is not found.
 
-## Adding CPM
-
-To add CPM to your current project, simply add the [latest release](https://github.com/cpm-cmake/CPM.cmake/releases/latest) of `CPM.cmake` or `get_cpm.cmake` to your project's `cmake` directory.
-The command below will perform this automatically.
-
-```bash
-mkdir -p cmake
-wget -O cmake/CPM.cmake https://github.com/cpm-cmake/CPM.cmake/releases/latest/download/get_cpm.cmake
-```
-
-You can also download CPM.cmake directly from your project's `CMakeLists.txt`. See the [wiki](https://github.com/cpm-cmake/CPM.cmake/wiki/Downloading-CPM.cmake-in-CMake) for more details.
-
 ## Updating CPM
 
-To update CPM to the newest version, update the script in the project's root directory, for example by running the command above.
+To update CPM to the newest version, update the script in the project's root directory, for example by running the same command as for [adding CPM](#adding-cpm).
 Dependencies using CPM will automatically use the updated script of the outermost project.
 
 ## Advantages