feat: Localization workflow improvements

[SuaYoo]

Partially addresses https://github.com/webrecorder/browsertrix/issues/1416

Changes

• Extracts translatable text strings in pre-commit hook
• Updates ternary pluralization to use pluralOf instead
• Generates XLIFF for Spanish

Manual testing

1. Regression test UI for number and plural formatting.
2. Verify staged changes to frontend/src will run localization string extraction on commit

[SuaYoo]

I worry a little that the precommit is getting too large (even without extracting strings it's a few seconds)

I'd be in favor of removing the lint check from pre-commit and just having it in CI, now that the webpack build shows linting errors?

[emma-sg]

Yeah, would be very down for that!