The vim counterpart to the existing Visual Studio Code extension.

Change-Id: I7ee59e212a31e81034362eb406f3ffdbb2447acb
Reviewed-on: https://chromium-review.googlesource.com/1180705
Commit-Queue: Timothy Gu <timothygu@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#55231}