Add dbaron to user handle mapping.

I don't know what this ends up being used for, but it seems like I
should probably be listed.

Change-Id: Ia95d36844da47b57242e9a69d019d0e282aebe2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2947882
Auto-Submit: David Baron <dbaron@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Chris Harrelson <chrishtr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#890452}

docs/user_handle_mapping.md

@@ -23,6 +23,7 @@ For Chromium contributors that have different nicks on other domains.
 | csharp            | csharp1         | csharp          |
 | cthomp            | cthomp          | cthomp          |
 | darin, fishd      | fishd           | darin           |
+| dbaron            |                 | ldavidbaron     |
 | dbeam             | danbeam         | dbeam           |
 | dmurph            | dmurph          | dmurph          |
 | dom               | domfarolino     | domfarolino     |