progressbar on web containers

[gliechtenstein]

Background web containers ship with progress bars built in.

This only applies to background web containers and not components.

Attributes

Additional attributes added through this PR:

• style
  • background: the default background color of the web container
  • progress: progress bar color

Example

{
  ...
  "body": {
    "style": {
      "background": {
        "type": "html",
        "style": {
          "background": "#ffffff",
          "progress": "#ff0000"
        }
      }
    }
  }
}