[WIP] Add ignoreContexts option

[fcurella]

This adds the ignoreContexts option, so external checks can be excluded as well.

I've pretty much copied the code for Checks, and replaced ->name() with ->context() and ->status() with ->state().

PS: I haven't written PHP in a decade, so I don't what current idiomatic code looks like nowadays. Feel free to nitpick :)

[fcurella]

Marking as WIP until I update all the tests

[WyriHaximus]

Awesome, looking forward to review this when it is ready 👍 !