Add SourcesJar and Unknown variants to AdditionalFileType enum

[TheDGOfficial]

This fixes the error that I was getting with the Fast Noise mod, when doing ./ferium scan with it in the mods folder, this would show up:

unknown variant `sources-jar`, expected `required-resource-pack` or `optional-resource-pack` at line 1 column 57679

When removing that mod from mods folder, the scan command would go on as normal.

Verified locally by using a local copy of ferinth with this change and compiling ferium with it, the scan command works when having the mod in mod folder.

[patch.crates-io]
ferinth = { path = "./ferinth" }

Fixes gorilla-devs/ferium#502

[CLAassistant]

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