feat: update CI configuration to install Node.js using nvm and remove pnpm action setup

Signed-off-by: Hendrik Ebbers <hendrik.ebbers@open-elements.com>

Author: hendrikebbers

package.json

@@ -9,7 +9,7 @@
   },
   "packageManager": "pnpm@11.3.0",
   "engines": {
-    "node": "24"
+    "node": ">=20"
   },
   "type": "module",
   "main": "./dist/index.js",