Add changelog entry for PR open-telemetry#3792 (FastAPI documentation improvements) (#2)

* Initial plan

* Add changelog entry for PR open-telemetry#3792

Co-authored-by: UltimatePlutoC <[email protected]>

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: UltimatePlutoC <[email protected]>

Author: Copilot

CHANGELOG.md

@@ -18,6 +18,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#3765](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3765))
 - Add `rstcheck` to pre-commit to stop introducing invalid RST
   ([#3777](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3777))
+- `opentelemetry-instrumentation-fastapi`: Add documentation section on environment variables, trace propagation, websockets, logging, and package links
+  ([#3792](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3792))
 
 - `opentelemetry-exporter-credential-provider-gcp`: create this package which provides support for supplying your machine's Application Default Credentials (https://cloud.google.com/docs/authentication/application-default-credentials) to the OTLP Exporters created automatically by OpenTelemetry Python's auto instrumentation. These credentials authorize OTLP traces to be sent to `telemetry.googleapis.com`. 
 [#3766](https://github.com/open-telemetry/opentelemetry-python-contrib/pull/3766).