Better documentation

[alvarouribe]

Description

The README.md page could be better explaining how to utilise this element

Expected outcome

Add a quick example or add a reference to the demo page to see an easy example.
I wish that all elements would have the same easy way to explain how to implement/use it
Maybe a small 4 step tutorial to use it

Actual outcome

explains the behaviour of the element without explain how to implement it

Documentation Affected

All

[valdrinkoshi]

@arthurevans FYI

[valdrinkoshi]

In general, behaviors should be used/implemented as explained here. In the catalog, it would be helpful to have this link available when the user is on a behavior.
In the catalog demo pages, it is currently not possible to "easily" access to the implementation of test elements (e.g. simple-overlay):

The only way to do that is to either open the dev-tools, or to click on source on the left drawer-panel of the catalog, and navigate to demo/simple-overlay.html.

[wyattallen]

The documentation should describe the focus-wrapping feature. Focus wrapping can cause issues such as #184 and #188 and are likely not an expected feature of an overlay. For my part, I had to dig into the source-code to discover the feature and diagnose my issue with it.