TOC added for readability

[j-d-carmichael]

This plugin is large with many headings, getting into the topic without a TOC is wasteful.

toc created with npx doctox

Platforms affected

Motivation and Context

Description

Testing

Checklist

• [x] I've run the tests to see all new and existing tests pass
• [x] I added automated test coverage as appropriate for this change
• [x] Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• [x] If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• [x] I've updated the documentation if necessary