Entity tagging tutorial

[bhancock8]

Is your feature request related to a problem? Please describe.

There have been a number of requests for an entity tagging tutorial.

Describe the solution you'd like

This tutorial will ideally show:

• how to create a high-recall set of entity candidates (e.g., with an off-the-shelf tagger, or some heuristic appropriate for the type of entity being classified)
• how to write LFs for weakly labeling these candidates
• how to train an appropriate classifier with the resulting training set

Additional context

This can be modeled after the pipeline used in snorkel-extraction, but should not rely on those tools. We'd like to demonstrate how this process can be down with a lighter touch pipeline that doesn't require use of a particular data model backend.

We would welcome contributions on this tutorial and would be happy to provide feedback. If you think you have an idea for an appropriate use case that could be used and would like to tackle it, you can post those here and we can start discussing it.