Add changelog for #272 (#277)

Author: arminru

semantic-conventions/CHANGELOG.md

@@ -4,6 +4,8 @@ Please update the changelog as part of any significant pull request.
 
 ## Unreleased
 
+- BREAKING: Make stability required (also: fix ref and extends, render badges on metrics).
+  ([#272](https://github.com/open-telemetry/build-tools/pull/272))
 - BREAKING: Make stability and deprecation independent properties.
   ([#244](https://github.com/open-telemetry/build-tools/pull/244))
 - Add backward-compatibility check mode.