Don't show <ddt-font-card-simple> when the layout card type is selected.
Started adding constant error messages.
Upgraded opentype.js.
Major changes to how fonts are created.

    * Fonts are now created using the Font.make static method.
      The method returns a promise.
    * We now use opentype.js to extract family name and font
      style from the font data.
    * CSS font face names are now generated using this metadata.
    * Font names in the UI are generated using this metadata.