[release] Add release notes for 2.13.2
[release] Add release notes for 2.13.2

Change-Id: I153e8f6ca05df97a3026491e5f6857780d718c56
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/202624
Reviewed-by: Michael Thomsen <5977a55c75bb4612004451a56b0b4c22d9d3311d@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk