Update CodeMirror to 5.13.5

public/vendor/codemirror/mode/gfm/index.html

@@ -47,7 +47,7 @@ Underscores_are_allowed_between_words.
 GFM adds syntax to strikethrough text, which is missing from standard Markdown.
 
 ~~Mistaken text.~~
-~~**works with other fomatting**~~
+~~**works with other formatting**~~
 
 ~~spans across
 lines~~

public/vendor/codemirror/mode/gfm/test.js

@@ -51,6 +51,12 @@
      "[comment ```]",
      "bar");
 
+  MT("fencedCodeBlockModeSwitchingObjc",
+     "[comment ```objective-c]",
+     "[keyword @property] [variable NSString] [operator *] [variable foo];",
+     "[comment ```]",
+     "bar");
+
   MT("fencedCodeBlocksNoTildes",
      "~~~",
      "foo",