[web] Add ellipsis on longer thread names

Summary:
This diff adds ellipsis to longer thread names

Before:
{F2974406}

After:
{F2974409}

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

web/navigation-panels/chat-thread-ancestors.css

@@ -11,6 +11,8 @@
   font-size: var(--l-font-18);
   font-weight: var(--semi-bold);
   white-space: nowrap;
+  text-overflow: ellipsis;
+  overflow: hidden;
 }
 
 .ancestorThreadsContainer {