* Add ASP.NET Core perf diagnostic tools list
* Add diagnostic tools doc to ToC
* A few minor phrasing tweaks
* Remove a few stray 'en-us' elements from links
* Fix typo in toc
* Update diagnostic-tools.md (#9898)
@mjrousos review and once we flesh out this PR we can merge into your PR and then into master. Excellent work, minor word-smithing.