Ignore .pyc files in third_party/[jinja2|markupsafe]

Also update the README.chromium to list the files added in these
directories.

Fixed: dawn:2301
Change-Id: Ia70528d890fb479dc17620cb06fc771116074c76
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5172588
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Auto-Submit: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1244448}
NOKEYCHECK=True
GitOrigin-RevId: da8822f42d506ad3a1968af90a931191195389af
2 files changed