Update changelog to add more information.

Author: mplatypus

changes/2219.feature.md

@@ -1 +1,5 @@
-Add support for built-in polls
+Add polls support:
+  - New rest endpoints: `RESTClient.fetch_poll_voters`, `RESTClient.end_poll`
+  - New Poll Objects: `Poll`, `PollLayoutType`, `PollResult`, `PollAnswer`, `PollMedia`
+  - New Builders: `PollBuilder`, `PollAnswerBuilder`
+  - New Events: `BasePollVoteEvent`, `PollVoteCreateEvent`, `PollVoteDeleteEvent`