resources: Add a few translated sections of the R800 User’s Manual.

Source images posted on Twitter by Japanese MSX user Kinnoji:

https://twitter.com/v9938
https://twitter.com/v9938/status/1124223395141308417
https://twitter.com/v9938/status/1124296770270351360
resources: Update Musical Memory Mapper manual to latest version.
msx_io_ports: Second PSG spans 10H-12H, and list devices which have it.
resources: Update links to the new MarkDown version on konamiman.github.io.
tsrdev_en: Start preformatted blocks on the same line.

To avoid an extra line of white space.
articles/(re)sources: Start preformatted blocks on the same line.

To avoid an extra line of white space.
css: Smaller preformatted block font on mobile.
articles/(re)sources: Start preformatted blocks on the same line.

To avoid an extra line of white space.
articles / sources: Use spaces instead of tabs in preformatted blocks.

Since tabs don’t show well on mobile, 4-space indentation is more compact.
documents: Remove XHTML conformance section.

It contained font tags, yuch.
css: Responsive design for mobile.
css: Formatting.
Remove two remaining (broken) map bullet references.
css: Remove the toc class.

Doesn’t seem to do anything.
css: Remove width from h1.

It’s a block element so already has the full width?
css: Remove hiding of second menu layer.

Since we removed it in 6503cfad2b7d.
Remove "msxasm" id from some bodies.

No idea what purpose it had being there.
Replace the map bullet list item icon with a text marker.

The list icon doesn’t work very well on mobile (looks too small).
content: Standard Content-Type header capitalisation.
content: Always include the HTML stylesheet link tag.

Since without it Firefox displays a flash of unstyled content.
(And without the <?xml-stylesheet?> Chrome does.)
Next