Add a globalOptions configuration property to setup custom rules and checks

[dwightjack]

This PR adds the ability to use the configureAxe function to setup custom checks and rules by adding a globalOptions property whose value will be passed to axe.configure.

It also updates the report log by checking for helpUrl before outputting the relative lines because custom rules might not have a help URL.

Reference: #112

@NickColley If you think this solution is fine, I will submit a PR to update the TypeScript definition as well.

[NickColley]

This is looking good thank you very much.

@kennygrubb do you have any thoughts on this proposal?

[kennygrubb]

Looks good to me. Thank you!

[NickColley]

Great I'll try and get this merged and released soon later today.

[dwightjack]

@NickColley @kennygrubb Just for reference: I submitted a PR to update the @types/jest-axe package as well: DefinitelyTyped/DefinitelyTyped#46122