DOT not validating correctly

[titusdecali]

I don't believe this was an issue before recently, however 'DOT' validation suddenly seems to return false when an address is actually correct.

I've added polkadot.js' official methodology for address validation as a stop-gap measure to solve validation only for DOT in the meantime, but this should be checked up on.

Here's a valid DOT address: 5GrpknVvGGrGH3EFuURXeMrWHvbpj3VfER1oX5jFtuGbfzCE

And the result from the package:

(otherwise, great package!)