implement basic GUI (monolith-gui)

Author: snshn

.github/workflows/ci.yml

@@ -32,7 +32,9 @@ jobs:
       uses: actions/checkout@v4
 
     - name: Build
-      run: cargo build --all --locked --verbose
+      run: |
+          cargo build --all --locked --verbose
+          cargo build --locked --verbose --bin monolith-gui --features="gui"
 
     - name: Run tests
       run: cargo test --all --locked --verbose