Exclude enum cases from type_name rule

[phelgo]

The type_name rule is currently being applied to enum cases. While the capital and alphanumerical requirements apply perfectly to enum cases, the minimum length may not. Examples like Direction.Up, Sixe.XL, Cardinal.SW should be allowed, and it feels cumbersome to add all these exceptions to the .swiflint.yml

[chadmoone]

I'm not sure about this. Potentially some default exceptions should be added for common two-letter words (up, in, id etc). But your other examples are acronyms/abbreviations, which most styleguides discourage to begin with. Personally, I don't see why enum cases should be treated differently than anything else in this regard. If your application really needs to have several two-letter enum types, you can always customize the rule to change the minimum allowed to 2.

[jpsim]

as of #660, we allow lowercase names for enum cases.