docs: some usage docs

docs/usage.rst

@@ -1,4 +1,80 @@
 Usage
 =====
 
-After installation, you can import and instantiate a client and then use the
+This package implements the Healthchecks.io Management and Ping APIs as documented here https://healthchecks.io/docs/api/.
+
+Sync
+----
+
+Instantiate a Client
+^^^^^^^^^^^^^^^^^^^^
+
+If you want to work with the healthchecks.io API for the SaaS healthchecks, you
+can create a client like below:
+
+.. code-block:: python
+
+   from healthchecks_io import Client
+
+   client = Client(api_key="myapikey", ping_key="optional_ping_key")
+
+If you are using a self-hosted healthchecks instance, you can set the api url when creating the client.
+
+.. code-block:: python
+
+   from healthchecks_io import Client
+
+   client = Client(api_key="myapikey",
+                   api_url="https://myhealthchecksinstance.com/api/",
+                   ping_key="optional_ping_key")
+
+
+Creating a new Check
+^^^^^^^^^^^^^^^^^^^^
+
+... code-block:: python
+
+    from healthchecks_io import Client, CheckCreate
+
+    client = Client(api_key="myapikey")
+
+    check = client.create_check(CreateCheck(name="New Check", tags="tag1 tag2")
+    print(check)
+
+Getting a Check
+^^^^^^^^^^^^^^^
+
+... code-block:: python
+
+    from healthchecks_io import Client
+
+    client = Client(api_key="myapikey")
+
+    check = client.get_check(uuid="mychecksuuid")
+    print(check)
+
+Pinging a Check
+^^^^^^^^^^^^^^^
+
+... code-block:: python
+    from healthchecks_io import Client
+
+    client = Client(api_key="myapikey")
+    result, text = client.success_ping(uuid="mychecksuuid")
+    print(text)
+
+Async
+-----
+
+If you want to use the client in an async program, use AsyncClient instead of Client
+
+
+
+... code-block:: python
+
+    from healthchecks_io import AsyncClient, CheckCreate
+
+    client = AsyncClient(api_key="myapikey")
+
+    check = await client.create_check(CreateCheck(name="New Check", tags="tag1 tag2")
+    print(check)