Lint .strings generation in CI

[mokagio]

Description

Same as wordpress-mobile/WordPress-iOS#19553 and Automattic/pocket-casts-ios#545

Adds a new CI check to give us faster feedback on whether the frozen .strings generation will work during code freeze. This way, if a PR breaks the process, we can address it immediately, without loss of context.

Testing instructions

Notice how the step passed in this build. You can see how the check catches an issue in this Jetpack/WordPress iOS demo build.

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

[wpmobilebot]

You can test the changes from this Pull Request by:

• Clicking here or scanning the QR code below to access App Center
• Then installing the build number pr8214-a07fa39 on your iPhone

If you need access to App Center, please ask a maintainer to add you.

[AliSoftware]

👌