Get current URL in customCrawl()

What is the current behavior? No information about current URL in customCrawl()

What is the motivation / use case for changing the behavior? I'm want to skip request, but add URL to csv for some files like zip, doc, pdf. My code that do it - https://github.com/viasite/sites-scraper/blob/59449b1b03/src/scrap-site.js#L240-L255

Proposal Add crawler to customCrawl: customCrawl: async (page, crawl, crawler)

I tried to store currentURL with requeststarted event, but it fail when more when concurrency > 1.

What do you think about it? I can make PR.