docs: add sample code for berserk python client

docs/api-testing.md

@@ -4,13 +4,29 @@ Consider using a lila-gitpod workspace while you develop your API integration be
 - Don't worry about messing anything up
 - If developing a bot, keep test games out of your bot's game history
 
-## Bot Development
+## Setup
+
 
 1. [Create your workspace](getting-started.md)
-2. Create an account for your bot
-3. Make port 8080 public, so you can access it from your bot's server
+2. [Make port 8080 public](sharing.md), so you can access it from the client.
+
+## Bot Development
+3. Create an account for your bot
 4. Point your bot to use your workspace's development site instead of `lichess.org`
 
  !!! info "Using lichess-bot"
 
   If you're using the [lichess-bot](https://github.com/ShailChoksi/lichess-bot) project, set the [`url` value in `config.yml`](https://github.com/ShailChoksi/lichess-bot/blob/master/config.yml.default) to your development site.
+
+## Client Development
+
+If you're using the Lichess [berserk](https://github.com/lichess-org/berserk) Python client, you can point it to your workspace's development site instead of `lichess.org`.
+
+```python
+import berserk
+
+client = berserk.Client(base_url="https://your-gitpod-instance.gitpod.io")
+
+profile = client.users.get_by_id('bobby')
+print(profile)
+```