Document how to add new scrapers

[stucka]

Scrapers for newly scraped states need to be manually added to .github/workflows in the etl.yml and extract.yml files.

[stucka]

warn-github-flow also needs to have a branch created with the state's postal abbreviation. Can do that through Github's web interface, code button, easier than anything.

warn-transformer needs sample data in tests/data/raw

scraper and transformer need to both be pushed, versions updated, and the new versions need to be into the pipenv of warn-github flow.