contributing/translations Adding Japanese translations and adjusting intro.md

[shimotmk]

Motivation for the change, related issues

Related issues #2198

Added a "Contributing to Translations" page and adjusted intro.md.

The Japanese documentation team has a custom of leaving the original text commented out and translating it immediately after.

Example:
https://github.com/jawordpressorg/gutenberg/blob/trunk/docs/README.md?plain=1

This makes it easier to check the differences when the original text is updated.

Command to compare the original text with Japanese

Example: intro.md

diff -y --suppress-common-lines packages/docs/site/docs/main/intro.md packages/docs/site/i18n/ja/docusaurus-plugin-content-docs/current/main/intro.md

---

When I put a comment out at the beginning of the md file, the Markdown title was rendered.
Therefore, I wrote the translated language first, and then the original text.

before	after

If this method works, I would like to contact the Japanese documentation team and increase the number of translated pages of the Japanese documentation.

[adamziel]

Let's see if the method works!

[shimotmk]

Thanks for the review 🙌
It works fine!
https://wordpress.github.io/wordpress-playground/ja/contributing/translations