Cypress Accessibility docs updates

[marktnoonan]

This PR:

• Adds yesterday's Results API updates to the Cypress Accessibility Changelog
• Add note about where to find the underlying axe-core version
• Accessibility intro page
  • Adds new Top Guide about detecting changes
  • Updates button styles for better spacing between them and around the icons.
  • Updates intro to mention seeing only new issues
• Adds "Read the guides" to the Get Started docs as the last step
• Adds "Detect and manage changes" guide brining together use cases for Analytics/Enterprise Reporting, the Results API, and Branch Review
• Updates the Results API documentation and type information to describe the new Views and Score data

[cypress]

cypress-documentation    Run #353

Run Properties:   Passed #353  •  50cd780af0: fix punctuation

Project	cypress-documentation
Branch Review	marktnoonan/a11y-docs-updates
Run status	Passed #353
Run duration	08m 34s
Commit	50cd780af0: fix punctuation
Committer	marktnoonan
View all properties for this run ↗︎

---

Test results
Failures	0
Flaky	0
Pending	0
Skipped	0
Passing	300
View all changes introduced in this branch ↗︎

UI Coverage  10.99%
Untested elements	2374
Tested elements	3

Accessibility  96.9%
Failed rules	1 critical   4 serious   4 moderate   0 minor
Failed elements	29

[tbiethman]

Updates related to the results API return type and usage look good to me 👍