Provide list of supported locales when lazy loading

[lukashass]

Clear and concise description of the problem

When eagerly loading the locales a list of supported locales is provided by useI18n().availableLocales.

There is no such list when lazy loading the locales since availableLocales only includes loaded locales.

Suggested solution

In https://github.com/lukashass/woodpecker/blob/1bfb9a322f9f8b94ec223afc7eb9085d54f3a16b/web/vite.config.ts#L34-L53 I used a vite virtual module that provides a list of supported locales derived from the filenames in the vueI18n include path.

I think this might be a good feature to be included in the vite plugin (or unplugin?)

Alternative

A manual list of supported locales is of course possible, but not really desirable IMHO.

Additional context

No response

Validations

• [X] Read the Contributing Guidelines.
• [X] Read the README
• [X] Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.