Adds a manual dispatch trigger to the container image publish workflow
in case there's any event/trigger hiccup in GitHub, otherwise we'd have
to delete and re-create a given release to kick-off the build/publish
pipeline again. This is just a safety measure (perhaps useful for
testing as well).

Assisted-by: Claude [sonnet 4.5]
Signed-off-by: Erik Skultety <eskultet@redhat.com>