Install.Type provides a rule that checks if a type is present
in the given module and if not, it adds it right after the imports.
For example, the rule
Install.Type.config "Frontend" "Magic" [ "Inactive", "Wizard String", "Spell String Int" ]
|> Install.customTyperesults in insertion the text below in the module "Frontend":
type Magic
= Inactive
| Wizard String
| Spell String IntConfiguration for rule.
Rule to add a type to a module if it is not present