Localization support for user/developer documents

Currently profiler itself [support l10n](https://github.com/firefox-devtools/profiler/tree/main/locales) but [user](https://github.com/firefox-devtools/profiler/tree/main/docs-user)/[developer docs](https://github.com/firefox-devtools/profiler/tree/main/docs-developer) are written only in English ad markdown and don't support any l10n (translation).

If you host documents on project specific site profiler.firefox.com instead of MDN (see also #1199), the site should support l10n.

You may use [docusaurus](https://docusaurus.io/docs/i18n/introduction) or any other framework with i18n support, or you should host user/developer documents on MDN since most document translation contributors are working on MDN.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-579)