HTML Content Extraction

### Problem Description
Crawler has the ability to store full pages as HTML, but often only subsets of HTML are useful. For example many sites have key content in xpath(*//main), and current tooling allows us to extract this as text, but not as HTML. Once extracted as HTML, additional work can be undertaken to convert to JSON or Markdown or semantically separated chunks of text.

### Proposed Solution
An option to have content extraction extract content as HTML.

### Alternatives
- Ingestion pipeline elements to handle HTML
- Painless capabilities to handle HTML
- Workarounds outside of platform