Add Entity form example

[Decipher]

Is your feature request related to a problem? Please describe.
As a developer I want to see an example of how I can build a headless content management application using Druxt.

Describe the solution you'd like

• Use existing docs/drupal backend
  • If required, configure OAuth and users/roles for demonstration purposes.
• Use or repurpose/rename the examples/entity-form Nuxt codebase
• Add a simple application interface using Vuetify: https://github.com/nuxt-community/vuetify-module
• Login with the DruxtAuth module using password workflow
• Show menu/folder tree on left side
• Show Filter Card list of Drupal Content Admin View in main pane
• Clicking on the card will open it into the View mode in the main pane
• All fields to have some form of inline editing/inline form mode
• Edit tab will display the content as a form

Describe alternatives you've considered

Additional context
I setup a prototype blog with content editing last year, it may have some useful code: https://github.com/Decipher/example-druxt-blog