Add missing dependency to linux build

Author: Ravbug

.github/workflows/build.yml

@@ -11,7 +11,7 @@ jobs:
         with:
           submodules: true
       - name: Install Dependencies
-        run: sudo add-apt-repository ppa:ubuntu-toolchain-r/test && sudo apt-get update && sudo apt-get install cmake g++-8 ninja-build -y --no-install-recommends 
+        run: sudo add-apt-repository ppa:ubuntu-toolchain-r/test && sudo apt-get update && sudo apt-get install cmake g++-8 ninja-build libgtk-3-dev -y --no-install-recommends 
       - name: Build
         run: mkdir -p build; cd build; export CC=/usr/bin/gcc-8; export CXX=/usr/bin/g++-8; cmake -G "Ninja" -DCMAKE_BUILD_TYPE=Release .. && cmake --build . --config release --target install 
       - name: Upload Artifacts