message: Document image requirements and the fact that the size of the
  dialog is the same as the image itself
diff: @@ -3,6 +3,9 @@ import Draggable from 'react-draggable';
  import { style } from 'typestyle';
  import { Button, Icon } from 'patternfly-react';
  +// The content of the graph legend is taken from the image in src/assets/img/graph-legend.png
  +// The size of content's dialog is the same as the image (it is fetched dynamically on this code)
  +// Any image format that can be displayed by a browser could be used.
  const graphLegendImage = require('../../assets/img/graph-legend.png');
  export interface GraphLegendProps {
  