build(deps): bump actions/checkout from 2 to 3 (#49)

Bumps [actions/checkout](https://github.com/actions/checkout) from 2 to 3.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v2...v3)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/dependabot.yml

@@ -5,3 +5,7 @@ updates:
     schedule:
       interval: "daily"
 
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "daily"

.github/workflows/html5validator.yml

@@ -0,0 +1,26 @@
+name: HTML5 Validator
+
+on:
+  push:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+
+    - uses: actions/checkout@v3 # Required will all actions
+
+    - uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: 3.1
+        bundler-cache: true # runs 'bundle install' and caches installed gems automatically
+
+    - name: Jekyll build
+      run: |
+        bundle exec jekyll build --drafts --profile
+
+    - name: Checks HTML5 validity
+      uses: Cyb3r-Jak3/html5validator-action@v7.1.1
+      with:
+        root: _site/
+        blacklist: n r or ir