Point GitHub link to gdext, add Sponsor link

Author: Bromeon

website/config.toml

@@ -36,10 +36,11 @@ title = "godot-rust"
 items = [
     { lang = "en", links = [
         { url = "/", name = "Home" },
-        { url = "https://github.com/godot-rust", name = "GitHub" },
+        { url = "https://github.com/godot-rust/gdext", name = "GitHub" },
         { url = "/book", name = "Book" },
         { url = "/docs", name = "API Docs" },
         { url = "/dev", name = "Devlog" },
+        { url = "https://github.com/sponsors/Bromeon", name = "♡" },
     ] }
 ]