Base64 and other types from Data

[adam-fowler]

What are the thoughts on extending the Base64 code to support all Collection types where Element is UInt8 instead of just Data. eg

extension Collection where Element == UInt8 {
    init?(
        base64Encoded: String,
        options: Data.Base64DecodingOptions
    ) {
    }

    func base64EncodedString(options: Data.Base64EncodingOptions) -> String {
        return "base64"
    }
}