The alert/callout blocks rendering has been changed in the previous few
commits, this adapts the test case that verifies them to the updated
output.
Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>
This adds a few test cases to exercise the alert block feature of the
markdown renderer, both the legacy GitHub style, and the modern one.
Signed-off-by: Gergely Nagy <forgejo@gergo.csillger.hu>