Update the ci.yml template in instructions (#46)

* Update the ci.yml template in Step 3

Bump actions/checkout from 3 to 4

* Edit YAML code block expressions

yaml to yml

.github/steps/1-add-a-test-workflow.md

@@ -32,7 +32,7 @@ First, let's add a workflow to lint our Markdown files in this repository.
 1. Name your workflow `ci.yml`.
 1. Update the workflow to remove all steps other than the "checkout" step.
 1. Add the following step to your workflow:
-   ```yaml
+   ```yml
    - name: Run markdown lint
      run: |
        npm install remark-cli remark-preset-lint-consistent

.github/steps/3-upload-test-reports.md

@@ -17,11 +17,11 @@ To upload artifacts to the artifact storage, we can use an action built by GitHu
 1. Edit your workflow file.
 1. Add a step to your `build` job that uses the `upload-artifacts` action.
 
-   ```yaml
+   ```yml
    build:
      runs-on: ubuntu-latest
      steps:
-       - uses: actions/checkout@v3
+       - uses: actions/checkout@v4
 
        - name: Run markdown lint
          run: |