Ability to pull a single language file from upstream

### Describe the problem

Solving conflicts in Weblate is a nightmare. This is evident when you try to mix Weblate translation with git based translation. It seems like the current options are:

- Merge Weblate upstream and fix the conflicts, but this forces users to commit possibly unwanted localization and make the upstream history dirty
- Hard reset Weblate from upstream, which requires a manual selection of the files to copy upstream before doing the reset

Both #98 and #5915 would definitely help with this issue, but since it seems like they won't be fixed any time soon, I propose what I think it's a simple solution which hopefully can be implemented without any particular implications.

### Describe the solution you'd like

Right now we have the ability to reset a Weblate component from upstream, but the impact of this is too broad. What I propose is to add the ability to pull a single language from upstream, by creating a new commit on the Weblate git head. This simple action would help solving conflicts on specific language files without affecting the other languages.

### Describe alternatives you've considered

_No response_

### Screenshots

_No response_

### Additional context

_No response_