[web] Add ellipsis on longer thread names

Summary:
This diff adds ellipsis to longer thread names

Before:

After:

Test Plan:

1. Create a community with a longer name
2. Verify that the ellipsis is added when thread name doesn't fit in browser window

Reviewers: inka, kamil

Reviewed By: kamil

Subscribers: ashoat, tomek

Differential Revision: https://phab.comm.dev/D13706