Support .mhtml

[jidanni]

On my chomebook with chrome I save a file, and it makes a "mhtml"
file. E.g., Downloads/Mapping USA 2024 _ OpenStreetMap US.mhtml .
Later offline, chrome has no problem opening that file.
But in lynx or w3m one just sees

$ w3m -dump /tmp/Untitled.mhtml | head | colrm 22
From: <Saved by Blink
Snapshot-Content-Loca
Subject: Untitled
Date: Wed, 6 Dec 2023
MIME-Version: 1.0
Content-Type: multipa
	type="text/ht
	boundary="---

I was thinking that lynx and w3m could be added to the long list of
supported browsers there in https://en.wikipedia.org/wiki/MHTML .

All that would be needed is if lynx and w3m just browsed the text/html part of the mhtml bundle, without requiring the user to unarchive that bundle into a directory first. No, no .mailcap file involved.