Duplicate of #31561 which already adds md, html, htm to the MEDIA: extractor regex with case-insensitive matching. #31754 was also closed as a duplicate of #31561.

Superseded by #34844, which consolidates this cluster.

This PR widens the extract_media extension allowlist, which is the right direction — but on its own it leaves the unconditional MEDIA:\s*\S+ strip in place, so a MEDIA: tag with any extension still outside the (now wider) list keeps getting deleted from the body before extract_local_files can pick up the bare path. #34844 fixes both halves: it unifies the two extractors onto a single shared extension set (MEDIA_DELIVERY_EXTS) AND replaces the loose strip with an extension-anchored one, so an unknown-extension path survives in the text instead of vanishing.

Closing as superseded — thanks for surfacing and helping pin down this bug; it was part of getting the full fix right. See #34844.