Call for case studies to be referenced on the homepage

[florisvdh]

Announcing that users of the package are welcome to cite their work on the homepage of {qgisprocess}. Users can be direct users or qgis users.

These references will be added under subsection 'In the wild'.

You can suggest citing your work by simply replying in this issue.

For now I propose the general format: <Reference to your work>. Source code: <URL>.