[web] Keep modal width constant
Summary:
Change modal size to large so that it doesn't change. Also, introduce ellipsis when an invite link is too long (copy button copies the whole content).
Test Plan: Check if the modal has the same width even when a link is long and copy button is clicked.
Reviewers: kamil, inka
Reviewed By: kamil
Subscribers: ashoat
Differential Revision: https://phab.comm.dev/D8484