Update changelog for mozilla#1516

Author: rosahbruno

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 [Full changelog](https://github.com/mozilla/glean.js/compare/v1.1.0...main)
 
+* [#1516](https://github.com/mozilla/glean.js/pull/1516): Implement the Custom Distribution metric type.
 * [#1514](https://github.com/mozilla/glean.js/pull/1514): Implement the Memory Distribution metric type.
 * [#1475](https://github.com/mozilla/glean.js/pull/1475): Implement the Timing Distribution metric type.
 * [#1500](https://github.com/mozilla/glean.js/pull/1500): BUGFIX: Update how we invoke CLI python script to fix `npm run glean` behavior on Windows.