Add test-reporter to Testing section

[dorny]

test-reporter displays test results from popular testing frameworks directly in GitHub:

• Parses test results in XML or JSON format and creates nice report as Github Check Run
• Annotates code where it failed based on message and stack trace captured during test execution
• Provides final conclusion and counts of passed, failed and skipped tests as output parameters

How it looks:

Supported languages / frameworks:

• .NET / xUnit / NUnit / MSTest
• Dart / test
• Flutter / test
• JavaScript / JEST

Support for other test results formats will be added later.