Installing libgtk-3-dev on Ubuntu

.github/workflows/checks.yml

@@ -31,7 +31,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Install system dependencies
-        run: sudo apt-get update && sudo apt-get install -y libatk1.0-dev librust-atk-dev
+        run: sudo apt-get update && sudo apt-get install -y libatk1.0-dev librust-atk-dev libgtk-3-dev
       - uses: actions/checkout@v2
       - name: All targets checks
         run: cargo check --workspace --all-targets