Add mdformat to the workflow in GitHub Actions

We would like to use mdformat as markdown checking.

I would propose that we use ydah/mdformat-action.
https://github.com/ydah/mdformat-action

.github/CONTRIBUTING.md

@@ -4,31 +4,31 @@ If you encounter problems or have ideas for improvements or new features, please
 
 ## Issue reporting
 
-* Check that the issue has not already been reported.
-* Check that the issue has not already been fixed in the latest code (a.k.a. `master`).
-* Check if the issue is a non-goal of RuboCop RSpec.
-* Be clear, concise, and precise in your description of the problem.
-* Open an issue with a descriptive title and a summary in grammatically correct, complete sentences.
-* Report the versions of `rubocop-rspec`, as well as the output of `rubocop -V`.
-* Include any relevant code to the issue summary.
+- Check that the issue has not already been reported.
+- Check that the issue has not already been fixed in the latest code (a.k.a. `master`).
+- Check if the issue is a non-goal of RuboCop RSpec.
+- Be clear, concise, and precise in your description of the problem.
+- Open an issue with a descriptive title and a summary in grammatically correct, complete sentences.
+- Report the versions of `rubocop-rspec`, as well as the output of `rubocop -V`.
+- Include any relevant code to the issue summary.
 
 ## Pull requests
 
-1.  Fork the project.
-2.  Create a feature branch.
-3.  Make sure to add tests.
-4.  Make sure the test suite passes (run `rake`).
-5.  Add a [changelog](https://github.com/rubocop/rubocop-rspec/blob/master/CHANGELOG.md) entry.
-6.  Commit your changes.
-7.  Push to the branch.
-8.  Create new Pull Request.
+1. Fork the project.
+2. Create a feature branch.
+3. Make sure to add tests.
+4. Make sure the test suite passes (run `rake`).
+5. Add a [changelog](https://github.com/rubocop/rubocop-rspec/blob/master/CHANGELOG.md) entry.
+6. Commit your changes.
+7. Push to the branch.
+8. Create new Pull Request.
 
 ## Creating new cops
 
-* Document examples of good and bad code in your cop.
-* Add an entry to `config/default.yml`. It's an ordered list, so be sure to insert at the appropriate place.
-* Run `bundle exec rake`. This will verify that the build passes as well as generate documentation and ensure that `config/default.yml` is up to date (don't forget to commit the documentation).
-* Add tests for as many use cases as you can think of. Always add tests for both bad code that should register an offense and good code that should not.
-* Common pitfalls:
-  * If your cop inspects code outside of an example, check for false positives when similarly named variables are used inside of the example.
-  * If your cop inspects code inside of an example, check that it works when the example is empty (empty `describe`, `it`, etc.).
+- Document examples of good and bad code in your cop.
+- Add an entry to `config/default.yml`. It's an ordered list, so be sure to insert at the appropriate place.
+- Run `bundle exec rake`. This will verify that the build passes as well as generate documentation and ensure that `config/default.yml` is up to date (don't forget to commit the documentation).
+- Add tests for as many use cases as you can think of. Always add tests for both bad code that should register an offense and good code that should not.
+- Common pitfalls:
+  - If your cop inspects code outside of an example, check for false positives when similarly named variables are used inside of the example.
+  - If your cop inspects code inside of an example, check that it works when the example is empty (empty `describe`, `it`, etc.).

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,25 +1,25 @@
 **Replace this text with a summary of the changes in your PR. The more detailed you are, the better.**
 
----
+______________________________________________________________________
 
 Before submitting the PR make sure the following are checked:
 
-* [ ] Feature branch is up-to-date with `master` (if not - rebase it).
-* [ ] Squashed related commits together.
-* [ ] Added tests.
-* [ ] Updated documentation.
-* [ ] Added an entry to the `CHANGELOG.md` if the new code introduces user-observable changes.
-* [ ] The build (`bundle exec rake`) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).
+- [ ] Feature branch is up-to-date with `master` (if not - rebase it).
+- [ ] Squashed related commits together.
+- [ ] Added tests.
+- [ ] Updated documentation.
+- [ ] Added an entry to the `CHANGELOG.md` if the new code introduces user-observable changes.
+- [ ] The build (`bundle exec rake`) passes (be sure to run this locally, since it may produce updated documentation that you will need to commit).
 
 If you have created a new cop:
 
-* [ ] Added the new cop to `config/default.yml`.
-* [ ] The cop is configured as `Enabled: pending` in `config/default.yml`.
-* [ ] The cop is configured as `Enabled: true` in `.rubocop.yml`.
-* [ ] The cop documents examples of good and bad code.
-* [ ] The tests assert both that bad code is reported and that good code is not reported.
-* [ ] Set `VersionAdded` in `default/config.yml` to the next minor version.
+- [ ] Added the new cop to `config/default.yml`.
+- [ ] The cop is configured as `Enabled: pending` in `config/default.yml`.
+- [ ] The cop is configured as `Enabled: true` in `.rubocop.yml`.
+- [ ] The cop documents examples of good and bad code.
+- [ ] The tests assert both that bad code is reported and that good code is not reported.
+- [ ] Set `VersionAdded` in `default/config.yml` to the next minor version.
 
 If you have modified an existing cop's configuration options:
 
-* [ ] Set `VersionChanged` in `config/default.yml` to the next major version.
+- [ ] Set `VersionChanged` in `config/default.yml` to the next major version.

.github/workflows/linting.yml

@@ -13,3 +13,14 @@ jobs:
           yamllint_comment: true
         env:
           GITHUB_ACCESS_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+  mdformat:
+    name: Mdformat
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - name: Mdformat
+        uses: ydah/mdformat-action@main
+        with:
+          number: true
+        env:
+          GITHUB_ACCESS_TOKEN: ${{ secrets.GITHUB_TOKEN }}