Format typescript with git cl format --js

Adds '.ts' to list of extensions to be handled by clang-format.

Change-Id: Ia00e59ba3ab617ebf248cfcf6df07dd98cdc14ce
Reviewed-on: https://chromium-review.googlesource.com/1120325
Reviewed-by: Ryan Tseng <hinoka@chromium.org>
Commit-Queue: Deepanjan Roy <dproy@chromium.org>

git_cl.py

@@ -5797,7 +5797,7 @@ def CMDformat(parser, args):
   diff_files = [x for x in diff_files if os.path.isfile(x)]
 
   if opts.js:
-    CLANG_EXTS.append('.js')
+    CLANG_EXTS.extend(['.js', '.ts'])
 
   clang_diff_files = [x for x in diff_files if MatchingFileType(x, CLANG_EXTS)]
   python_diff_files = [x for x in diff_files if MatchingFileType(x, ['.py'])]