Add Ask.map and Ask.map!

[Cody Allen]

Summary

This adds Ask.map! and a delayed Ask.map, which map the input to an Ask computation. This is analogous to Haskell's MonadReader.local, but more flexible, since it can map the type parameter. I thought about naming it Ask.local, which might help some Haskeller's find it, but I didn't think that was a particularly obvious name for FP newcomers. Most (maybe all?) of the other map functions in base are covariant maps, while this is a contravariant map. But Ask.map should be unambiguous since there can't be a covariant map for Ask (other than function composition on the output, but that's already covered by >>), and I don't think that naming it Ask.contraMap would be helpful to anyone.

Notable definitions:

• abilities.Ask.map!
• abilities.Ask.map!.test

Changes

  Here's what would change in the current namespace after the merge:
  
  Added definitions:
  
    1. abilities.Ask.map.doc      : Doc
    2. abilities.Ask.map!.doc     : Doc
    3. abilities.Ask.map!.example : Text
    4. abilities.Ask.map          : (a ->{g1} b) -> '{g2, Ask b} r -> '{g1, g2, Ask a} r
    5. abilities.Ask.map!         : (a ->{g1} b) -> '{g2, Ask b} r ->{g1, g2, Ask a} r
    6. abilities.Ask.map!.test    : [test.Result] (+1 metadata)

[Rúnar]

This is now in /main. Thanks! 🌈⭐