Include fastlane metadata in Transifex config

[ArnyminerZ]

Purpose

At some point, Fastlane metadata was removed from the Transifex config.

Short description

Add the resources back again, including the mapping to make sure r is not included in the lang codes.

Checklist

• The PR has a proper title, description and label.
• I have self-reviewed the PR.
• I have added documentation to complex functions and functions that can be used by other modules.
• I have added reasonable tests or consciously decided to not add tests.

[sunkup]

Looks ok, but when we did 349de85 did we forget to remove the "r" in the lang_map in the [main] section ?

[ArnyminerZ]

I will merge this PR, just because I think it's not worth it to think about this for a lot, since we will eventually migrate to Weblate