Update actions/checkout action to v6 (#109)

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

Author: renovate[bot]

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
           - ubuntu
           - windows
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: ./
       - if: failure() && runner.debug == '1'
         uses: mxschmitt/action-tmate@v3

.github/workflows/release.yml

@@ -15,7 +15,7 @@ jobs:
   release:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
       - uses: actions/setup-node@v6
         with:
           cache: npm