ci: install libgtk3 for build

.github/workflows/build.yml

@@ -16,7 +16,12 @@ jobs:
 
     steps:
     - uses: actions/checkout@v3
+    
+    - name: Install build deps
+      run: apt install libgtk-3-dev
+    
     - name: Build
       run: cargo build --verbose
+      
     - name: Run clippy
       run: cargo clippy --verbose