[F20] Initial dockerfiles for Tauto RTD

These will not build right now (as /supporting is missing), but they are
a starting point (more to come)

BUG=b:186635049
TEST=local testing

Change-Id: I280fa8f3241bcbfc7597acc43d29e28fd4a4f87f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2885995
Tested-by: Derek Beckett <dbeckett@chromium.org>
Commit-Queue: Derek Beckett <dbeckett@chromium.org>
Reviewed-by: Keith Haddow <haddowk@chromium.org>
Reviewed-by: Katherine Threlkeld <kathrelkeld@chromium.org>