Associate file extensions

[gdementen]

I just tested associating a few file extensions with the editor. This mostly works and, contrary to what I thought, WITHOUT admin priviledges. There are a few oddities that I need to investigate whether they are issues with pixi or with the original menuinst code that conda uses (AFAICT, pixi uses rattler_menuinst which is just a port of menuinst to rust, so I suppose the behavior should be the same -- unsure what code (micro)mamba uses or wether they support menus/file association).

• the icon is the "generic executable" one, not the one specified. A pity but not a blocker.
• the files type appear in File Explorer as .<ext> LArray Editor.AssocFile.<ext> file which is quite strange/ugly/confusing but not a blocker.
• running the editor with (a) file(s) as argument should open the File Explorer not load them (because that's faster and we support a lot more formats that way)
• we should only associate files for which our users probably do not have a viewer installed: .h5, .feather, ...