feat: add k-launcher-ui-egui crate for enhanced UI

- Introduced a new crate `k-launcher-ui-egui` to provide a graphical user interface using eframe and egui.
- Updated the workspace configuration in `Cargo.toml` to include the new crate.
- Implemented the main application logic in `src/app.rs`, handling search functionality and user interactions.
- Created a library entry point in `src/lib.rs` to expose the `run` function for launching the UI.
- Modified the `k-launcher` crate to include a new binary target for the egui-based launcher.
- Added a new main file `src/main_egui.rs` to initialize and run the egui UI with the existing kernel and launcher components.

crates/k-launcher-ui-egui/src/lib.rs

@@ -0,0 +1,12 @@
+mod app;
+
+use std::sync::Arc;
+
+use k_launcher_kernel::{AppLauncher, SearchEngine};
+
+pub fn run(
+    engine: Arc<dyn SearchEngine>,
+    launcher: Arc<dyn AppLauncher>,
+) -> Result<(), eframe::Error> {
+    app::run(engine, launcher)
+}