Reorganize docs for easier deploys

With the current docs directory setup, I'm making too many mistakes and have to manually address path changes and directory moves on deploy. This makes for a frustrating experience developing locally and shipping releases. With this PR, we're basically back to the same setup from v3—duplicating the dist directory into our docs directory. Not the most ideal, but very straightforward for me as the release manager.

site/_includes/callout-danger-async-methods.md

@@ -0,0 +1,8 @@
+{% capture callout %}
+#### Asynchronous methods and transitions
+
+All API methods are **asynchronous** and start a **transition**. They return to the caller as soon as the transition is started but **before it ends**. In addition, a method call on a **transitioning component will be ignored**.
+
+[See our JavaScript documentation for more information.]({{ site.baseurl }}/docs/{{ site.docs_version }}/getting-started/javascript/)
+{% endcapture %}
+{% include callout.html content=callout type="danger" %}