Release 12.5.0 into trunk

[iangmaia]

Releasing new version 12.5.0.

What's Next

PR Author: Be sure to create and publish a GitHub Release pointing to trunk once this PR gets merged,
copy/pasting the following text as the GitHub Release's description:

### New Features

- The `ios_lint_localizations` action now accepts a `fail_on_strings_not_in_base_language` parameter (defaulting to `true`) to control whether to report violations when finding strings in translations that are not present in the base language. [#631]

### Internal Changes

- The library now uses immutable literals, via `# frozen_strings_literal: true`. This may result in runtime issues that we will address ASAP once discovered [#626]