Add Wall of Browser Bugs entry for twbs#18365

See http://bugzil.la/1228802

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Author: cvrebert

docs/_data/browser-bugs.yml

@@ -68,6 +68,16 @@
   origin: >
     Bootstrap#793
 
+-
+  browser: >
+    Firefox
+  summary: >
+    `focus` events should not be fired at the `document` object
+  upstream_bug: >
+    Mozilla#1228802
+  origin: >
+    Bootstrap#18365
+
 -
   browser: >
     Chrome (OS X)