Update actions/checkout action to v6 (#92)

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

Author: renovate[bot]

.github/workflows/lint.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: true
 

.github/workflows/pages.yml

@@ -12,7 +12,7 @@ jobs:
     runs-on: ubuntu-24.04
     container: hugomods/hugo:reg-git-0.152.2
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@v6
         with:
           submodules: true