AI-GCS: Create reference dataset for indexing (reusing PurlDB and SWH)

[pombredanne]

We need to create a reference dataset of code for actual indexing, reusing PurlDB and/or SWH as possible.

The data should be tagged with PURLs and extra metadata so we know the origin of the code.

Given the large size of this data set, it may not be possible to publish the whole data itself. We can instead publish the list of all inputs used, including URLs, and document the process used to create this data.
The outcome should be:

• An open data dataset description with basic documentation, ideally published on Zenodo.