feat: onRedirect

[ronag]

[ronag]

@szmarczak started a bit in case you want to have a try a it. I think it's mostly the test missing.

[szmarczak]

I wonder if it would be ok to include this.history, statusCode and headers as well.

• this.history can be used to detect infinite loops
• statusCode & headers - for handling 300 Multiple Choices

[Linkgoron]

maybe onRedirect should be able to "short-circuit" the redirection (e.g. by returning false)?