Allow to split conditions different validators in separate checks

[Jackenmen]

One GitHub app can create multiple checks, so it would be nice if mergeable would support this (unless it does and I just don't know how set it up then I'll be thankful for any tips)

[shine2lay]

@jack1142 Currently we can't do this yet and this is only because context between each When: 'event' is shared. After we add logic to run each When in it's own context, this will be available by doing something like this.

- When : 'pull_request.*'
    validate: # First ruleset 
    pass: 
      do: checks # first check
- When : 'pull_request.*'
    validate: # Second ruleset
    pass:
      do: checks # second check

[shine2lay]

I've been doing a bit of research on this, it seems we'll need to provide different 'name' in the checks in order to create separate checks, otherwise they get overwritten. what do you think about adding a name field for each when @jusx ?