Unpadded Base64

The `unpaddedbase64` library provides functionality to encode and decode Base64 strings that explicitly omit the '=' padding characters. While RFC 4648 specifies that Base64 should be padded to a multiple of 4 bytes, many protocols choose to leave out this padding. The current version is 2.1.0, released in March 2021, and the library has an infrequent release cadence.