Marketplace: indicate translation level of plugins

We want to indicate a plugins supported locales when viewing the plugin data.

This can be hidden for english users but should be displayed if a user has non english browser configs or a non english user locale.

- [ ] Show supported locales on plugin view screen
- [ ] Maybe: warn if plugin translations are not available in their locale
- [ ] Differentiate between localized support help and translation support. e.g. "Available in `es`, `ja`, `de`. Support available in `en`."

Context pdh6GB-IF-p2#comment-2164

Review the marketplace plugin view screen and its existing locale or translation data; no file or test is named, so first locate those entry points. Done should include the agreed display of supported locales for non-English configurations and a decision on the optional warning and support-versus-translation distinction.

Written by the indexing model from the issue text.