feat: add Swedish language support in settings and translations

[snowfruit]

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Inspired by this #370 .

I think this PR introduces the first version of the Swedish language translation.

The current version is translated and proofread by me. Some phrases were searched for to find suitable alternatives.

I have not used github in a long time so I hope this is correct.

[CLAassistant]

All committers have signed the CLA.

[nekename]

Hey, thanks for this :)

I'll take a look when I get back to this project