Easier upper/lowercase transformation

[mrleblanc101]

Hi,
Should this lib ship with upper/lowercase transromation token by default ?à
This is a very common use case, and it require to change from data-mask="@#@ #@# " to v-maska[options] syntax just to add this feature.
Ex:

{
    mask: '@#@ #@#',
    tokens: {
        '@': { pattern: /[a-zA-Z]/, transform: (chr) => chr.toUpperCase() },
    },
}

I think we should add 2 new token a that would lowercase everything and A that would uppercase everything.
If someone need to use the letter a or A in their mask, they can escape it.

This would allow us to do:
data-mask="A#A #A#" to get H0H 0H0 instead of h0h 0h0