Define a watchlist for wpt-tools and add lpz+watch to it

Change-Id: I3c5f11a1d217b1c65af4b49a72d0fa31b9d3a862
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1890985
Commit-Queue: Luke Z <lpz@chromium.org>
Commit-Queue: Robert Ma <robertma@chromium.org>
Auto-Submit: Luke Z <lpz@chromium.org>
Reviewed-by: Robert Ma <robertma@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710871}

WATCHLISTS

@@ -1909,6 +1909,9 @@
     'windows_sandboxing': {
       'filepath': 'sandbox/win/',
     },
+    'wpt_tools': {
+      'filepath': 'third_party/blink/web_tests/external/wpt/tools/',
+    },
     'x11': {
       'filepath': 'content/browser/renderer_host/backing_store_x\.' \
                   '|chrome/browser/chromeos/input_method/xkeyboard\.' \
@@ -2708,6 +2711,7 @@
                          'msramek+watch@chromium.org'],
     'webui_backend': ['dbeam+watch-webui-backend@chromium.org'],
     'windows_sandboxing': ['wfh+watch@chromium.org'],
+    'wpt_tools': ['lpz+watch@chromium.org'],
     'x11': ['sadrul@chromium.org',
             'yusukes+watch@chromium.org'],
     'zlib': ['cblume+zlib@chromium.org'],