Enhance and improve the accessibility example

 - remove the `accesskey` attributes. Use of the `accesskey` is generally
not recommended as it tends to cause conflicts with AT software and user
settings
 - change the scripted accesskey to go to the map to a regular skiplink
 - use script to inject the buttons below the map, if the map were to fail for lack of javascript support the buttons should not be there either. These should be buttons (and not hyperlinks) because they provide an action not a navigation
 - update the docs
 - add an empty `alt` attribute to the logo since it is strictly
decorative (this should probably be done sitewide)