Add basic slint app

inköpslista-gui/src/main.rs

@@ -0,0 +1,14 @@
+// Prevent console window in addition to Slint window in Windows release builds when, e.g., starting the app via file manager. Ignored on other platforms.
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
+
+use std::error::Error;
+
+slint::include_modules!();
+
+fn main() -> Result<(), Box<dyn Error>> {
+    let ui = App::new()?;
+
+    ui.run()?;
+
+    Ok(())
+}