Enabled highlighting of contributions with a Processing icon

This fixes [#2580](https://github.com/processing/processing/issues/2580).

In order to highlight a contribution, either the authorList must contain "The Processing Foundation", or the contribution must contain "Starred" in its category. Safe guards have been added to ensure that the contribution isn't highlighted, even if "Starred" is present in the .properties file of the contribution, unless "Starred" is present in the contributions.txt file as well.