Add steimel to blimp watchlist

BUG=

Review-Url: https://codereview.chromium.org/2351773002
Cr-Commit-Position: refs/heads/master@{#419522}

WATCHLISTS

@@ -1461,7 +1461,8 @@
                'perumaal+watch-blimp@chromium.org',
                'scf+watch-blimp@chromium.org',
                'shaktisahu+watch-blimp@chromium.org',
-               'sriramsr+watch-blimp@chromium.org'],
+               'sriramsr+watch-blimp@chromium.org',
+               'steimel+watch-blimp@chromium.org'],
     'blink': ['blink-reviews@chromium.org'],
     'blink_accessibility': ['aboxhall@chromium.org',
                             'dmazzoni@chromium.org',