update the changelog

CHANGELOG.md

@@ -17,6 +17,11 @@
 - Compat data mapping for modern Android WebView to Chrome moved from targets parser directly to compat data
 - Depracate `core-js-builder` `blacklist` option in favor of `exclude`
 
+##### 2.6.12 [LEGACY] - 2020.11.26
+- Added code points / code units explicit feature detection in `String#at` for preventing breakage code which use obsolete `String#at` proposal polyfill
+- Added `OPEN_SOURCE_CONTRIBUTOR` detection in `postinstall`
+- Added Drone CI detection in `postinstall`
+
 ##### 3.7.0 - 2020.11.06
 - `String#replaceAll` moved to the stable ES, [per June TC39 meeting](https://github.com/tc39/notes/blob/master/meetings/2020-06/june-2.md#stringprototypereplaceall-for-stage-4)
 - `Promise.any` and `AggregateError` moved to the stable ES, [per July TC39 meeting](https://github.com/tc39/notes/blob/master/meetings/2020-07/july-21.md#promiseany--aggregateerror-for-stage-4)