various documentation improvements

[davidjgoss]

Helps address:

• Scenario result exception is not available in HookScenarioResult #1245
• using a tsconfig.json file with cucumber-js #1139

[davidjgoss]

@charlierudolph are you okay with the changes here?

[charlierudolph]

Yep. Looks good thanks for the updates. Was a bit apprehensive about the function definition wrapper docs as that was originally only intended for wrapping generators before async/await existed. Really want to get the before / after step hooks in, so we can kill that.