[WIP] add rule for alphabetic characters, as well as space.

[Bound3R]

Hi, :sunglasses:

I'm create this for cases like text validations as open fields, the alpha rule is insufficient for me, it can be solved with a custom rule obviously, but being such a common case in fields like description or names, I decided to add this rule because I suppose that many people you can use it to get it ready.

This is still in development - missing full test :computer:

any comments are welcome