Merge #481: Show error when proxied image cannot be loaded

e578718 feat: [#409] show error image when proxied image (Jose Celano)
84816bf chore(deps): add dependency to generate images from text (Jose Celano)

Pull request description:

  The error is an image with a text explaining the error. The reason is I don't want the sanitizer to inject other elements into the DOM. The sanitizer replaces images `img` with proxied images (images from the proxy the Index API).

  The current behavior when the proxy does not work or the extension is not valid is just not showing the image. This PR generates an error image in those cases. The same way browsers show "broken images" when they can load images.

ACKs for top commit:
  josecelano:
    ACK e578718

Tree-SHA512: 5c2b4b3c2d6ba12cc9dc389e31fe64666cc00b1301e0eff44da29c151339dabee43073dca25fd023189b013f0e2a468092471948325faefab444f6bed25bc227

Author: josecelano