Switch Scribe-i18n from git subtree to git submodule

[andrewtavis]

Terms

• I have searched open and closed issues
• I agree to follow Scribe-iOS' Code of Conduct

Issue

Note

This is a mirror issue of scribe-org/Scribe-Android#527

We are moving Scribe-i18n from a git subtree to a git submodule across Scribe-Android, Scribe-iOS and scri.be.

This change allows contributors to work on i18n keys and values directly while developing features, commit and push changes to the Scribe-i18n repository, and keep translation updates closely aligned with feature work.

Work includes removing the existing subtree, adding Scribe-i18n as a submodule, updating contributor documentation, and ensuring CI/build pipelines support submodules.

[andrewtavis]

@catreedle, maybe we can look into #563 while we work on this? :)

[andrewtavis]

Closed by #568 🚀 Amazing work here, @catreedle! 😊