Create a document on how to use Drupal Check and report Drupal 8 deprecations

[mglaman]

Working doc at MidCamp: https://docs.google.com/document/d/1UnVzmQhCv9_IT0-u-tjvWPDR-QQAU31ij2iKkio8U3U/edit#

Modules list: https://docs.google.com/spreadsheets/d/1-W0k4vhdmw7ugzRdSa9orEc43_D5l6PPvUcrB8bw_-0/edit#gid=0

[josephdpurcell]

PR is created with some usage: https://github.com/mglaman/drupal-check/blob/feature/readme/README.md#usage

Also, https://github.com/mglaman/drupal-check/wiki/Drupal-9-Readiness#im-a-module-maintainer

And then a document for resolutions to issues: https://github.com/mglaman/drupal-check/wiki/Deprecation-Error-Solutions

[TravisCarden]

In a similar vein, the findability of both this project and its documentation should be considered. For example, the most probable entry point for new users may be the blog post Testing your Drupal code base for deprecated code usage with PHPStan, which doesn't refer to this project at all. You might consider adding a conspicuous note to that post indicating that there's a simpler setup for most people and pointing them here.

[mglaman]

@TravisCarden I can update my blog post! This tool came out a month or so later

[mglaman]

I updated the blog post. Closing this as we have some resources on the repo.