Fixed pl-PL locale name bug

[retrowaver]

Polish locale pl-PL was written as pl-Pl (lowercase L) in a few spots in code, causing errors when using it. Therefore I replaced all pl-Pl to pl-PL.

[profnandaa]

That's a good catch! 👍

1. Did we have tests for this? Can that be changed too?
2. How can we support backward compatibility if we have folks already using pl-Pl in production right now?

[retrowaver]

1. I'd propose a test comparing names of locales in alpha, alphanumeric, commaDecimal and phones, looking for names that are the same in case insensitive comparison, but different in case sensitive one. The thing is I have zero experience with js tests / more advanced js in general, so I'm not sure if it's the right approach / it is even possible / how to actually do it.
2. I think decimal['pl-Pl'] = decimal['pl-PL']; should do the trick (in validator.js around line 580 ).

[chriso]

Thanks for the PR 😄 I'll create an alias for backwards compatibility.