docs: How do I "add ecad"? (ember-learn#1668)

- Adding section does not have any isntructions.
- Should I just `ember install`? Or are there any other steps?

Author: MichalBryxi

tests/dummy/app/templates/docs/standalone-apps.md

@@ -21,6 +21,8 @@ In my case, I did it as an [in repo addon](https://github.com/ember-animation/em
 
 ## 4. Add `ember-cli-addon-docs` to your docs app.
 
+You can follow the <DocsLink @route="quickstart">quickstart guide.</DocsLink>
+
 ## 5. Set `documentingAddonAt`
 
 Configure the docs app's `ember-cli-build.js` to tell ember-cli-addon-docs to point at the addon: