Update actions/checkout to v6 (#221)

* Update actions/checkout to v6

* Add dependabot setting

Author: yutannihilation

.github/dependabot.yml

@@ -0,0 +1,6 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"

.github/workflows/update_github_meta.yaml

@@ -14,7 +14,7 @@ jobs:
       GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v6
 
       - uses: r-lib/actions/setup-r@v2
         with: