jwk function
Implementation
JWK jwk(String pub, [String? d]) {
final coords = pub.split('.');
final data = JWK.from(
crv: 'P-256',
kty: 'EC',
x: coords[0],
y: coords[1],
d: d ?? "",
ext: true,
key_opts: d != null ? ['sign'] : ['verify'],
);
return data;
}