Merge pull request #16116 from RudyLu/keyboard/Bug967857-Bengali_UI

Bug 967857 - Add specific CSS rules for Bengali - Probhat keyboard to
r=timdream(cherry picked from commit 31af75189710e8930be943dc96a4ccd339a6010f)

Conflicts:
	apps/keyboard/style/keyboard.css
Bug 970235 - [v1.3] Xfail test_ftu_skip_tour() with Bug 965912
Merge pull request #16122 from chirarobert/v1.3_xfail_ftu_test

Bug 970235 - [v1.3] Xfail test_ftu_skip_tour() with Bug 965912