File Naming missing lang tag

[Kedryn]

Pre-flight

• I searched existing issues and this isn't a duplicate
• I checked the roadmap and this isn't already planned

Problem

In the File Naming import settings, there is no tag for the language.
It would be useful to have it in the name for foreing books.

Proposed solution

add a {lang} tag

Alternatives considered

No response

Additional context

No response