function hextob64u(s) {
    if (s.length % 2 === 1) {
        s = '0' + s;
    }
    return Base64.base64ToBase64Url(Base64.hexToBase64(s));
}
Returns decoded keys in Hex format for use in crypto functions.
Supports modulus/exponent-style keys.

@param {object} key the security key
@returns