Add context comments to i18n key

[obulat]

Fixes

Fixes #617 by @obulat

Description

This PR adds comments to the i18n strings that are used inside a full sentence:

{
  /**
  Interpolated into hero.disclaimer.content:
   _{license}_ part of "All Openverse content is under a _{license}_ or is in the public domain."
  */
  license: "Creative Commons license",
}

This allows the translators to correctly select the word forms that match the full sentence.

It would be great if we could automate the creation of such comments, but I didn't find an easy way of doing that.
Still, having such comments is very important for accurate translations.

Testing Instructions

Run the app locally using just frontend/run dev
You should not see any warnings about i18n keys missing in the console on any page of the site.

Also, look through the strings and see check that the comments look correct.

Checklist

• My pull request has a descriptive title (not a vague title likeUpdate index.md).
• My pull request targets the default branch of the repository (main) or a parent feature branch.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• I added or updated tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.
• I ran the DAG documentation generator (if applicable).

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[zackkrida]

This is very thoughtful. It looks like you removed some unused strings too? LGTM.

[dhruvkb]

The primary reason for switching to JSON5 was to provide such helpful context to the translators! Thanks for utilising it.

[obulat]

This is very thoughtful. It looks like you removed some unused strings too? LGTM.

Yes, I did remove unused strings and renamed a string in the comments (updated from kebab-case to camelCase). Forgot to add this in the PR descriptions.