docs: add usage docs

docs/index.rst

@@ -5,8 +5,8 @@
 
 ``aiohttp-oauth2-client``: OAuth2 support for ``aiohttp`` client
 ================================================================
-This package adds support for OAuth 2.0 authorization to the ``ClientSession`` class of the ``aiohttp`` library.
-It handles retrieving access tokens and injects them in the Authorization header of HTTP requests as a Bearer token.
+This package adds support for OAuth 2.0 authorization to the :obj:`~aiohttp.ClientSession` class of the ``aiohttp`` library.
+It handles retrieving access tokens and injects them in the *Authorization* header of HTTP requests as a Bearer token.
 
 **Features**:
 

docs/usage.rst

@@ -1,4 +1,45 @@
 Usage
 =====
 
+Getting started
+---------------
+
+Begin by importing the relevant modules, like the OAuth2 client and grant. Also import ``asyncio`` for running async code::
+
+    import asyncio
+    from aiohttp_oauth2_client.client import OAuth2Client
+    from aiohttp_oauth2_client.grant.device_code import DeviceCodeGrant
+
+
+Then create an :obj:`~aiohttp_oauth2_client.grant.common.OAuth2Grant` and :obj:`~aiohttp_oauth2_client.client.OAuth2Client` object and perform a HTTP request to a protected resource. We use the
+Device Code grant in this example::
+
+    async def main():
+        async with DeviceCodeGrant(
+                token_url=TOKEN_URL,
+                device_authorization_url=DEVICE_AUTHORIZATION_URL,
+                client_id=CLIENT_ID,
+                pkce=True
+        ) as grant, OAuth2Client(grant) as client:
+            async with client.get(PROTECTED_ENDPOINT) as response:
+                assert response.ok
+                print(await response.text())
+
+
+    asyncio.run(main())
+
+
+The client and grant objects can be used as async context managers. This ensures the proper setup and cleanup of
+associated resources.
+
+
+Grant configuration
+-------------------
+Each grant type has specific configuration options associated with it.
+Extra parameters can be provided, which will then be used in the authorization process.
+
+* :obj:`~aiohttp_oauth2_client.grant.authorization_code.AuthorizationCodeGrant`
+* :obj:`~aiohttp_oauth2_client.grant.client_credentials.ClientCredentialsGrant`
+* :obj:`~aiohttp_oauth2_client.grant.resource_owner_password_credentials.ResourceOwnerPasswordCredentialsGrant`
+* :obj:`~aiohttp_oauth2_client.grant.device_code.DeviceCodeGrant`