* docs(i18n): add Bulgarian README
Add a complete Bulgarian (bg) translation of the README and list it in
every README language bar and the website language inventory.
Register bg with a pending website catalog that uses the labeled,
nonindexable English fallback, with the fallback notice translated.
Regenerate the shared language picker and hreflang links and refresh
messages.pot.
* docs(i18n): clarify Bulgarian project code license scope
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Co-authored-by: morluto <76467478+morluto@users.noreply.github.com>