Update versions of some actions in use

Author: gcotelli

.github/workflows/markdown-lint.yml

@@ -5,9 +5,9 @@ jobs:
     name: runner / markdownlint
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: markdownlint
-        uses: reviewdog/action-markdownlint@v0.1
+        uses: reviewdog/action-markdownlint@v0
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           fail_on_error: true

.github/workflows/unit-tests.yml

@@ -6,7 +6,7 @@ jobs:
    unit-tests:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
       - name: Run tests using Docker
         working-directory: .docker
         run: ./docker-tests.sh