Add user facing documentation

[saulshanabrook]

We should add some user facing documentation that outlines how to use this plugin.

[tgeorgeux]

Outline:

• [ ] Intro: This is an exploration, not the end product.
• [ ] Installation & Updating installation (jupyterlab extension update)
  • [ ] Connecting to the Data Registry
• [ ] Introduction to Linked Data.
  • [ ] Reference out to linked data
  • [ ] Show Datasets.yaml file
• [ ] How to navigate the Graph.
  • [ ] Click links.
  • [ ] Manual URL input.

[saulshanabrook]

https://json-ld.org/