Document Cypress.log interface

[jennifer-shehane]

The Cypress.log interface is how a user can modify the "reporter" left side and display commands / pending / take snapshots / indicate failure, etc.

This is currently undocumented and needs to be documented.

[richdouglasevans]

Over here Brian writes:

There's a bunch of improvements I wanted to make to Cypress.log() before officially documenting it.

I've been idly scrolling through this filtered list of open tickets looking for one to pick up and this one seems a possible candidate. Have the improvements that Brian mentions been made and is this ticket good to go?

@jennifer-shehane Totes open to a steer from you about which tickets I can pick up and work on. I've been steering clear of bigger ones only because I don't want to step on the toes of the Cypress team 😄

[jennifer-shehane]

Closing as duplicate of #1839