sphinx extension for creating panels in a grid layout

 A sphinx extension for creating document components optimised for HTML+CSS.
 .
   * The panels directive creates panels of content in a grid layout, utilising
     both the Bootstrap 4 grid system, and cards layout
   * The link-button directive creates a click-able button, linking to a URL or
     reference, and can also be used to make an entire panel click-able
   * The dropdown directive creates toggle-able content
   * The tabbed directive creates tabbed content
   * opticon and fa (fontawesome) roles allow for inline icons to be added.