bump release to 0.6.4

Author: bilelmoussaoui

gtk4/Cargo.toml

@@ -10,7 +10,7 @@ license = "MIT"
 name = "gtk4"
 readme = "README.md"
 repository = "https://github.com/gtk-rs/gtk4-rs"
-version = "0.6.3"
+version = "0.6.4"
 rust-version = "1.64"
 [lib]
 name = "gtk4"