option to hide join/parts entirely

[matrixbot]

Created by @ matthew:matrix.org.

[fuzzy76]

Would love this. Getting mentioned 24 hours ago in a busy bridged IRC channel makes for a terrible session of scrolling to find the context. Hiding joins/parts for those channels would help a lot.

[richvdh]

might want to hide changes of avatars/displayname too.

[Chaos99]

While I'm fully behind this and duplicated it in #3476, isn't the focus unnecessary small here?
If you are going to implement any filter stage for messages before display, why not make it customizable in the first place? Just let the user add regex for the message data fields they want to see/not see per room.
(With some templates like joins/leaves/name changes).

[t3chguy]

I have started on this, got the filtering stage hooked up to a new part of UserSettingsStore, just need to make the UI for its settings now.

@Chaos99 with the structure of a Matrix event I think regex would not be a very good method, plus when filtering a large amounts of event it could introduce delay
The way I've done it so far allows you to hide any arbitrary eventType or msgType

[ara4n]

@t3chguy is this on a branch somewhere? @kegsay may be able to pick it up today