fix: fix some base32 parsing issues by using go standard library instead of regex

[jamesatkin-myndup]

Fixes Or Enhances

Some strings were failing to be parsed by the previous RegEx based validation. This now uses the Go base32 module (part of the standard library) to more reliably decode the field.

Make sure that you've checked the boxes below before you submit PR:

• Tests exist or have been written that cover this particular change.

@go-playground/validator-maintainers

[coveralls]

coverage: 74.3% (+0.009%) from 74.291%
when pulling 14dc595 on jamesatkin-myndup:master
into a947377 on go-playground:master.

[coveralls]

coverage: 74.297% (+0.006%) from 74.291%
when pulling c17835f on jamesatkin-myndup:master
into a947377 on go-playground:master.