Change types entry

[Pikachu920]

Is your feature request related to a problem? Please describe.
I'm always frustrated when I am unable to enforce change types at parse time when possible.

Describe the solution you'd like

expression something:
  change types: number, location
  get:
    # ...
  set:
    # ...

Describe alternatives you've considered
Checking the change value's type at runtime, but this doesn't allow for parse time errors.

[btk5h]

I'm planning on allowing acceptable change types to be set per change mode.

expression something:
  set number, location:
    # ...