The current Base64 library offers support only for base64 encoding:

https://github.com/OpenZeppelin/openzeppelin-contracts/blob/5420879d9b834a0579423d668fb60c5fc13b60cc/contracts/utils/Base64.sol

However, with the advent of Foundry, there's also the need for decoding base64-encoded strings in test files.

At the moment, OpenZeppelin users are forced to go look for a solution elsewhere, e.g. in Solady, which provides both encoding and decoding.

It would thus be helpful to provide a decode function on top of encode.