Add an extra step to detail Docker environment clean up

.github/steps/1-create-the-workflow-file.md

@@ -25,7 +25,7 @@ We'll start by creating the workflow file to publish a Docker image to GitHub Pa
 
 1. Open a new browser tab, and work on the steps in your second tab while you read the instructions in this tab.
 1. Navigate to the **Code** tab.
-1. From the **main** branch dropdown, click on the **cd** branch.
+1. From the **main** branch dropdown, click on the `cd` branch.
 1. Navigate to the `.github/workflows/` folder, then select **Add file** and click on **Create new file**.
 1. In the **Name your file...** field, enter `publish.yml`.
 1. Add the following to the `publish.yml` file:

.github/steps/6-clean-up-docker.md

@@ -0,0 +1,31 @@
+<!--
+  <<< Author notes: Step 6 >>>
+  Start this step by acknowledging the previous step.
+  Define terms and link to docs.github.com.
+-->
+
+## Step 6: Clean up Docker container and image
+
+Excellent! Now it's time to clean up your Docker environment! :broom:
+
+Let's stop :stop_sign: the Docker container we have running and (optionally) remove the image. :wastebasket:
+
+### :keyboard: Activity: Stop your container
+
+1. Find your running container by typing `docker ps`.
+1. Use the following command to stop your container:
+   ```bash
+   docker stop CONTAINER_ID
+   ```
+1. Replace `CONTAINER_ID` with your image's Container ID.
+1. Press **Enter**.
+
+### :keyboard: Activity: (optional) Remove your image
+
+1. List Docker images on your system by typing `docker image ls`.
+1. Use the following command to remove your Docker image:
+   ```bash
+   docker rmi IMAGE_ID
+   ```
+1. (optional) For the sake of verification, you can re-run `docker image ls` to confirm your Docker image has been removed.
+1. _We can't automatically verify this step for you, so please continue on to the next step below!_

.github/workflows/3-merge-your-pull-request.yml

@@ -55,10 +55,10 @@ jobs:
           fetch-depth: 0 # Let's get all the branches.
 
       # In README.md, switch step 3 for step 45X.
-      - name: Update to step 45X
+      - name: Update to step 456X
         uses: skills/action-update-step@v2
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           from_step: 3
-          to_step: 45X
+          to_step: 456X
           branch_name: cd