Add all reporters to doc/API.md

[WilcoFiers]

Expectation: All available reporters in axe-core are listed in the API docs.

Actual: only v1 and v2 are documented.

[straker]

None of the reporters describe what they do exactly. Do you have a summary of them? Looking at the code this is my best guess:

• raw to return the raw result data without formating: axe.configure({ reporter: "raw" });
• raw-env to return the raw result data with environment data: axe.configure({ reporter: "raw-env" });
• no-passes to return only violation results: axe.configure({ reporter: "no-passes" });
• na (no idea what this reporter does)

[jeankaplansky]

Doc is present and accounted for, but no one specifically validated @straker's best guess. @WilcoFiers, @JKODU? Did he guess right? I'm moving this ticket to QA in the meantime. Please make a new sprint-ready ticket for any required corrections for 7/1. Thanks!

[somaalapati]

Now rest of the 3 reporting types have been added to doc/API.md file. So, closing this ticket. (will close this after getting confirmation on expected details from @WilcoFiers.