Charts categories

[iosonosempreio]

Specify charts categories. Now all charts have the category "dispersion".

[mikima]

Prepared charts categories, but they should be correclty parsed in the interface as array and not as strings

[iosonosempreio]

Update category metadata. Make it a strings array.

Currently on master branch:

import icon from './matrixplot.svg'
import thumbnail from './heatmap_thumb.svg'

export const metadata = {
  name: 'Matrix Plot',
  thumbnail,
  icon,
  category: 'Network',
  description:
    'It allows comparison of two categorical dimensions, disposing them on the horizontal and vertical axes. Each glyph (square or circle) represents a possible correlation among the two dimensions. Associated quantitative variables can be represented with size and/or color.'
}

@mikima