src: support new message fields (#3388)

* src: Update channel pattern

* src: Remove useless non-capture group

* src: it's as though we're starting fresh

* src: Bring this up to date for reals now

* src: typings and a bug fix

* src: Add crossposted channels to message mentions

* src: Requested changes and add typings

* src: Move Object.keys outside loop

* typings: Fix enum being exported when it shouldn't

* src: Consistency with roles and users

* docs: Correct docstring for MessageFlags#flags

* docs: Correct docstring for MessageMentions#crosspostedChannels

* docs: Suggestions
Co-authored-by: SpaceEEC

* src: Reset flags to 0 if no flags are received on MESSAGE_UPDATE

src/index.js

@@ -20,6 +20,7 @@ module.exports = {
   DataStore: require('./stores/DataStore'),
   DiscordAPIError: require('./rest/DiscordAPIError'),
   HTTPError: require('./rest/HTTPError'),
+  MessageFlags: require('./util/MessageFlags'),
   Permissions: require('./util/Permissions'),
   Speaking: require('./util/Speaking'),
   Snowflake: require('./util/Snowflake'),