docs/parse-support-md: Handle BulletList

Commit d638e304f1 introduced a bullet list, but parse-support-md
choke on it as it doesn't know what to do about it.

Introduce ri_BulletList() so that r_content() will find this new
function and call it instead of calling process_unknown().

Reported-by: Julien Grall <julien@xen.org>
Fixes: d638e304f1 ("SUPPORT.MD: Fix matrix generation after 43c416d0d8 and 77c39a53cf5b")
Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Tested-by: Julien Grall <jgrall@amazon.com>
Acked-by: Julien Grall <jgrall@amazon.com>

docs/parse-support-md

@@ -218,6 +218,13 @@ sub ri_DefinitionList {
     }
 }
 
+sub ri_BulletList {
+    # Assume a paragraph introduce this bullet list, which would mean that
+    # ri_Para() has already been called, and there's nothing else to do about
+    # the caveat.
+    return;
+}
+
 sub process_unknown {
     my ($c, $e) = @_;
     $had_unknown = Dumper($e);