Sync script for translation repos

[tesseralis]

Description

Create a sync script that updates translation repositories based on the current state of the source repo.

Usage:

yarn run sync [language code]

Behavior

1. Creates a new PR that merges the source repo gatsby-i18n-source to the current head of the translation repo, committing all merge conflicts
2. Adds comments referring to the changes in the source between the last sync and now, to help translators decide what content needs to be updated.

Next steps

• Don't create a PR if there is an existing one
• Watch source repo and run on all translation repos when there are updates
• Automatically merge the PR if there are no conflicts
• Documentation for how to resolve a sync script (pending (docs) Split translation guide into multiple pages for clarity #21254)
• Decide if we want to commit non-conflicting files separately

Examples

• Japanese: Sync with gatsby-i18n-source @ 9df3cf4 gatsby-ja#155
• Hindi: Sync: (sync) Sync with gatsby-i18n-source @ fd3df38 gatsby-hi#44 / Conflicts: (sync) Resolve conflicts with gatsby-i18n-source @ fd3df38 gatsby-hi#43

Documentation

#21753

Related issues

Fixes: #21250

[AishaBlake]

@tesseralis this looks good and I've seen it work. I've also read through the WIP docs in #21753. Do you intend to work on any more of the "next steps" in this PR or do you feel comfortable moving forward? I think I'd prefer to merge with the functionality this has now and then work in smaller chunks to tackle additional work.

[tesseralis]

@AishaBlake I'd like to merge this in now and work on the "next steps" in a different PR.

[AishaBlake]

I'm happy with this and ready to merge.

[AishaBlake]

Should probably also check in with @LekoArts. Lennart, feel free to merge if you're good with this! I'd also like to get #21753 in soon after.

[LekoArts]

👍

(Seem like the checks fail though)

[tesseralis]

@LekoArts it's only starters validate, it's failing because of npm audits.