Event tracking

[joedolson]

Add an event tracker that gives site owners insight into how the WP Accessibility tools are being used on their site. Changes made, use of font resizing and high contrast toggling, etc.

[joedolson]

Basic outline of tracking:

• Register REST API endpoint to save data
• Pass a JSON object with the URL, an array of issue IDs, and any additional data about the issue for that page.
• Log again only if the data for that page changes (different count, different fixes applied, etc.)

Send to me if opted in:

• md5 hash of domain with object containing md5 hashed URL & issues logged.

[joedolson]

Have added the stats tracking for the local site, but no mechanism to push those to me yet.