Could we fuzztest random Fluid keyboard inputs?

[StachuDotNet]

Start with a random AST, and check for a few things:

• works same in main editor or FF editor (though FF editor has many known breakages)
• where there's a Pat and an Expr that should behave the same - test that
  (create an equivalent pat and expr and see that they're augmented in the 'same' way)
• ?

Just a misc. thought - not sure how this would go