Add an FAQ entry on acceptable use of Relay

[Vinnl]

New feature description

Like #1540, but applied to the React codebase from #1518 (this PR merges into that PR's branch). To get ourselves used to reviewing React PRs 🙂

Screenshot (if applicable)

How to test

Go to the /faq page, verify that the new question is shown there.

Checklist

• l10n dependencies have been merged, if any. Not yet: Add FAQ entry on acceptable use mozilla-l10n/fx-private-relay-l10n#60
• All acceptance criteria are met.
• I've added or updated relevant docs in the docs/ directory.
• All UI revisions follow the coding standards, and use Protocol tokens where applicable (see /static/scss/libs/protocol/css/includes/tokens/dist/index.scss).
• Commits in this PR are minimal and have descriptive commit messages.

[Vinnl]

This is a small peculiarity of @fluent/react: it can only replace <tags> in translation strings via the <Localized> wrapper component, not via the useLocalization hook (that provides the l10n object).

The way that component works is: it takes its child element (<p />, in this case), and replaces its contents with the contents of the Fluent string (faq-question-acceptable-use-answer-a-html).

Also note that vars shouldn't actually be necessary: if the string just says <my-tag>acceptable use policy</my-tag>, then we could add my-tag to elems and set whatever attribute we need on the element there, just like we set the href attribute on the <a> element we replace the a tag with. However, because this string is also used on the current site, I had to use the <a href="{ $url }" { $attrs }> trick too.

[maxxcrawford]

Quick note for @codemist and @Vinnl: I created a new label for any React focused issues or issues while we are managing both front ends. If we need a label for the Django front-end, lmk and we can make another tag too.

[maxxcrawford]

I have one non-blocking change!

[maxxcrawford]

suggestion: Can open all FAQ links in a new tab?

From the Djagon frontend, we add the following attrs to each link in the FAQ: https://github.com/mozilla/fx-private-relay/blob/main/static/js/app.js#L362-L373

Note that the noopener may no longer be necessary.

[Vinnl]

7b1a05b

Note that the linter (configured to use the recommended default rules by ESLint and Next.js) added both rels automatically on commit. Better safe than sorry, I suppose :)