Update actions/checkout action to v6 (#5)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/cmake.yml

@@ -17,7 +17,7 @@ jobs:
         os: [ubuntu-latest, windows-latest, macos-latest]
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
 
       - name: Configure CMake
         run: cmake -B ${{github.workspace}}/builds/${{ runner.os }} -DCMAKE_BUILD_TYPE=${{env.BUILD_TYPE}}