Add changelog for 0.21.3

Author: TobiGr

fastlane/metadata/android/en-US/changelogs/969.txt

@@ -0,0 +1,8 @@
+• Allow installation on external storage
+• [Bandcamp] Added support for displaying the first three comments on a stream
+• Only show 'download has started' toast when download is started
+• Do not set reCaptcha cookie when there is no cookie stored
+• [Player] Improve cache performance
+• [Player] Fixed player not automatically playing
+• Dismiss previous Snackbars when deleting downloads
+• Fixed trying to delete object not in list