[chore] document that the zipkin encoding extension ships with contrib (open-telemetry#41591)

Author: atoulme

extension/encoding/zipkinencodingextension/README.md

@@ -4,11 +4,12 @@
 | Status        |           |
 | ------------- |-----------|
 | Stability     | [alpha]  |
-| Distributions | [] |
+| Distributions | [contrib] |
 | Issues        | [![Open issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aopen%20label%3Aextension%2Fzipkinencoding%20&label=open&color=orange&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aopen+is%3Aissue+label%3Aextension%2Fzipkinencoding) [![Closed issues](https://img.shields.io/github/issues-search/open-telemetry/opentelemetry-collector-contrib?query=is%3Aissue%20is%3Aclosed%20label%3Aextension%2Fzipkinencoding%20&label=closed&color=blue&logo=opentelemetry)](https://github.com/open-telemetry/opentelemetry-collector-contrib/issues?q=is%3Aclosed+is%3Aissue+label%3Aextension%2Fzipkinencoding) |
 | [Code Owners](https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/CONTRIBUTING.md#becoming-a-code-owner)    | [@MovieStoreGuy](https://www.github.com/MovieStoreGuy), [@dao-jun](https://www.github.com/dao-jun) |
 
 [alpha]: https://github.com/open-telemetry/opentelemetry-collector/blob/main/docs/component-stability.md#alpha
+[contrib]: https://github.com/open-telemetry/opentelemetry-collector-releases/tree/main/distributions/otelcol-contrib
 <!-- end autogenerated section -->
 
 This extension supports marshaling and unmarshaling Zipkin data representing traces.

extension/encoding/zipkinencodingextension/metadata.yaml

@@ -5,7 +5,7 @@ status:
   class: extension
   stability:
     alpha: [extension]
-  distributions: []
+  distributions: [contrib]
   codeowners:
     active: [MovieStoreGuy, dao-jun]
 

reports/distributions/contrib.yaml

@@ -96,6 +96,7 @@ components:
         - redis_storage
         - sigv4auth
         - text_encoding
+        - zipkin_encoding
     processor:
         - attributes
         - cumulativetodelta