Merge pull request #19727 from twbs/bugzilla-1264125

Add http://bugzil.la/1264125 to Wall of Browser Bugs
[ci skip]

docs/_data/browser-bugs.yml

@@ -98,6 +98,16 @@
   origin: >
     Bootstrap#18365
 
+-
+  browser: >
+    Firefox
+  summary: >
+    Fire `transitioncancel` event when a transition is canceled
+  upstream_bug: >
+    Mozilla#1264125
+  origin: >
+    Mozilla#1182856
+
 -
   browser: >
     Firefox (Windows)