[WIP] List of suggestions for next Examples revamp

[droumis]

The contribution process is still primarily for HoloViz developers and is not really geared towards users who are not already software engineers. The exposed steps should be robust and simplified.

• Remove the option to use intake catalogs as a data ingestion method.
• Require that each example notebook create or source its data as part of the notebook (rather than allowing for data ingestion spec in the anaconda yml).
• Combine the tags.yml approach (used for website section categorization) with anaconda-project.yml's project 'labels' (currently mainly for holoviz package labels but is unconstrained and include some other things. These labels are used as filter buttons on the website and appear in the card footer).
• Is the use of anaconda-project a barrier for users? Consider having two contribution guides, one for casual users which simplifies (and limits certain configurations, e.g. resource profile) the process, and the other guide like what we have.
• merge 'thumbnails' with 'assets' directories
• remove the requirement to add a small version of a dataset to the test_data directory
• Add an 'original authors' field to acknowledge the initially conceived version and a separate 'authors' field to designate any additional authors post-conception. Also, add a metadata field for 'contributors' for those who directly added value to the example at any point, but much less so than an author. I think these additional fields better reflect reality without adding too much overhead and will help to align incentives and reward maintenance, modernization, and example evolution.