Don't let LTR usernames jumble RTL watchlists

Adding unicode-bidi: embed isolates them from other
fields like time, title, summary etc.

This is particularly relevant to showing Wikidata changes.

Change-Id: I5c3f53318fcbfed75b0df9e24e5ff8636c0fea4b
Merge "Don't let LTR usernames jumble RTL watchlists"