Implement 'Jump to first unread message' feature in rooms using m.fully_read marker

[MurzNN]

Seems at now RiotX miss Jump to first unread message feature, that scroll room timeline to first unread message. This is very important feature for most of users, especially in rooms with many members. Also X action for mark all as read.

I can't find issue about implementing this feature, only about displaying read markers #84 in phase2. But displaying markers is not so important comparing to Jump to first unread message feature.

For implement jumping we can use m.fully_read marker from spec https://matrix.org/docs/spec/client_server/r0.4.0#fully-read-markers

So I suggest to implement Jump to first unread message earlier, than displaying read markers.

[MurzNN]

Ow, I look at wrong place https://github.com/vector-im/riotX-android/projects/1
Phase0 is finished, Phase1 is almost too: https://github.com/vector-im/riotX-android/milestones
So phase2 is good place, together with #84

[jtagcat]

Note: some users prefer to jump to first, without losing their last read position (read few first unread, then jump back to their last position)

[jtagcat]

Addition to ny comment: In discord I hate when I reply to someone, after sending the message, it automatically moves me to the bottom. RiotX already opens a new page what you can close with x, when you click jump to 1st.

[bmarty]

Related to #84

[bmarty]

-> next sprint

[bmarty]

Implemented by #592

[progserega]

"Jump marker" some times freeze:

Video:
https://yadi.sk/i/qq-2DY3YCAAunQ

RiotX version: 0.7.0 G-b1099

[MurzNN]

Same problem for me with unmarkable as read messages sometimes. Workaround is scroll down to next messages (for hide problematic message from screen) and use "jump to unread"