docs(python): Add documentation for the Python SDK Async Transport Option

Author: srothh

docs/platforms/python/configuration/options.mdx

@@ -320,6 +320,22 @@ sentry_sdk.init(
 
 </SdkOption>
 
+<SdkOption name="transport_async" defaultValue='None'>
+An experimental fully async transport. Requires the asyncio integration and the [httpcore[asyncio]](https://www.encode.io/httpcore/async/) library. If enabled, the Sentry SDK has to be initialised while an event loop is running.
+
+```python
+sentry_sdk.init(
+    _experiments={
+        "transport_async": True,
+    },
+    integrations=[
+        AsyncioIntegration(),
+    ],
+)
+```
+
+</SdkOption>
+
 ## Tracing Options
 
 <SdkOption name="traces_sample_rate" type='float' defaultValue='None'>