Add-on Marketplace for GraphPolaris

The add-on API allows developers to create and publish new add-ons to the new GraphPolaris marketplace. Here, users will be able to add visualisation and machine learning add-ons to their workspace, to use on their data. The final product also includes a standalone marketplace that allows for browsing, searching and filtering add-ons, created by third-party developers. This addition allows anyone to expand the possibilities of analysing graph data endlessly within the application.