Refresh look of file format / external link icons

[salty-horse]

The file format icons in the external links feel extremely ancient.

I think it's no longer appropriate to represent a web-hosted game with an icon for "HTML file".

There are also missing icons for things like images, and it would be nice to fill those gaps. Maybe even have dedicated icons for storefronts like Steam and itch.io.

Discussion: https://intfiction.org/t/refresh-look-of-file-format-external-link-icons/72269

[salty-horse]

Easy replacement Glulx icon:
Old:
New:

[salty-horse]

This is how to edit a file icon:
http://localhost:8080/fileformat?id=25&edit

Some problems:

• Only GIFs are supported.

• Identical images are not reused between formats, and are stored separately.

• Images are returned without caching, even though they are used in many places.

• This comment doesn't make sense:

  This icon is used as a fallback if the. File Type doesn't have an associated icon.

  These are the file type icons. In viewgame, the only thing that is checked before it is the "OS icon".