Add relnotes xlink (#387)

Author: theletterf

docs/docset.yml

@@ -4,6 +4,7 @@ cross_links:
   - opentelemetry
   - elastic-agent
   - apm-agent-python
+  - elastic-otel-python
 toc:
   - toc: release-notes
   - toc: reference/edot-python

docs/reference/edot-python/toc.yml

@@ -9,4 +9,6 @@ toc:
   - file: migration.md
   - file: overhead.md
   - title: Troubleshooting
-    crosslink: docs-content://troubleshoot/ingest/opentelemetry/edot-sdks/python/index.md
+    crosslink: docs-content://troubleshoot/ingest/opentelemetry/edot-sdks/python/index.md
+  - title: Release notes
+    crosslink: elastic-otel-python://release-notes/index.md