docs: add pnpm/bun to JS language (#28572)

Author: igas

docs/usage/javascript.md

@@ -1,10 +1,10 @@
 ---
 title: JavaScript
-description: JavaScript (npm/Yarn) Package Manager Support in Renovate
+description: JavaScript (npm/Yarn/pnpm/Bun) Package Manager Support in Renovate
 ---
 
 # JavaScript
 
 Renovate supports upgrading JavaScript dependencies specified in `package.json` files.
 
-`npm`, `yarn`, and `pnpm` are all supported.
+`npm`, `yarn`, `pnpm` and `bun` are all supported.