i18n(sr-Cyrl, sr): Add Serbian (Cyrillic and Latin) translation

[AAnzel]

Updated translation and corrected locale names after the following failed pull request: https://github.com/pop-os/firmware-manager/pull/135.

[n3m0-22]

Are you seeing both the Cyrillic and Latin translations on your end? As it is right now no matter what I set the system to I only see the Latin. I was able to see the Cyrillic only after removing the sr directory renaming the sr-Cyrl to sr and then building. I have yet to be able to get both Cyrillic and Latin translations to work in the same build.

[AAnzel]

@n3m0-22, I do not, but I thought it was something on my end. I believe the sr directory is used as a default or a fallback language. One way to fix this would probably be to rename sr into sr-Latn. I am trying to figure out how to proceed and am open to suggestions. Could you also please tell me whether I should use the locale codes as defined here https://manpages.ubuntu.com/manpages/bionic/man3/DateTime::Locale::Catalog.3pm.html or this page is deprecated?

[n3m0-22]

I would think that page is still good as there are subsections at the top for 22.04 and 22.10. I'll look into it and see if I can come up with a solution. Thanks for the info.

[n3m0-22]

The directory sr-Cyrl is fine as is. The directory sr needs to be changed to sr-Latn. That has both translations working on my end.

@AAnzel Once these changes are made, I can retest this PR.

[AAnzel]

@n3m0-22, thanks a lot for figuring out the solution. I hope the last commit (https://github.com/pop-os/firmware-manager/pull/136/commits/3140f9abc7eb09b363fcc5b793518bf22b68c362) solves the problem completely.

[AAnzel]

It is my pleasure. :)