Handle Removed Associations in mimeapps.list

[tleydxdy]

for details, see https://specifications.freedesktop.org/mime-apps-spec/latest/associations.html

[Anomalocaridid]

Thank you for your issue! I also appreciate you linking a specification for the functionality you want!

After bashing my head against it for a bit, it seems that implementing this might take a while. Essentially, not handling Removed Associations let me (and probably a lot of past contributors as well) make some assumptions when writing code that are proving difficult to undo.

I have also been fairly busy with other things in my life, so it may take me a while to get back around to it.

However, rest assured that I certainly plan to implement this eventually.