docs: add russian to supported languages

* Update documentation to reflect added Russian translation support

Co-authored-by: Copilot <copilot@github.com>

Author: saturneric

README.md

@@ -66,6 +66,7 @@ GpgFrontend currently supports an array of languages including:
 - German
 - Italian
 - Spanish
+- Russian
 
 And these translations are contributed by our community: [SHOW](TRANSLATORS)