Add GitHub Action for mdbook
Add GitHub Action for mdbook

BUG=b:199688855
TEST=run at personal account

Change-Id: I7e44424deccf64be5fdf0d14d24109c3245e37c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3159885
Reviewed-by: Dennis Kempin <cd09796fb571bec2782819dbfd33307f65b1c778@google.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Keiichi Watanabe <815e4e8f7c92a23424d7c3f51ead622bcedbc720@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm