docs: add usage examples

Author: classabbyamp

docs/index.rst

@@ -1,8 +1,51 @@
 NetAuth for Python
 ==================
 
+.. highlight:: python
+
 A `NetAuth <https://netauth.org>`_ client library for Python.
 
+To install: ``pip install netauth``
+
+Usage
+~~~~~
+
+This library centers around the :class:`NetAuth` object::
+
+   na = netauth.NetAuth("netauth.example.org")
+
+   try:
+       resp = na.system_status()
+       print(resp)
+   except netauth.error.NetAuthRpcError as e:
+       print(f"Request failed: {e}")
+
+   na.close()
+
+:class:`NetAuth` can also be used as a context manager and be initialized from a NetAuth configuration file::
+
+
+   with netauth.NetAuth.with_config(Path("/etc/netauth/config.toml")) as na:
+       try:
+           resp = na.system_status()
+           print(resp)
+       except netauth.error.NetAuthRpcError as e:
+           print(f"Request failed: {e}")
+
+For interactive or dynamic applications, operations that require authentication can use a callback to retrieve the user's secret::
+
+   def secret_cb() -> str:
+       return getpass(prompt="Secret: ")
+
+   with netauth.NetAuth("netauth.example.org", entity="demo", secret=secret_cb) as na:
+       try:
+           na.entity_kv_add("demo", "foo", ["bar", "baz"])
+       except error.NetAuthRpcError as e:
+           print(f"Request failed: {e}")
+
+API
+~~~
+
 .. currentmodule:: netauth
 
 .. autoclass:: NetAuth