docs: Document pad types

And update the plugins doc cache
0 jobs for !160 with document_pads
latest yaml invalid error detached

Found errors in your .gitlab-ci.yml:

  • Remote file `https://gitlab.freedesktop.org/gstreamer/gst-ci/raw/master/gitlab/ci_template.yml` could not be fetched because of HTTP code `503` error!
You can also test your .gitlab-ci.yml in CI Lint