JWS signature algorithm
key for verification. CryptoKey object, PKCS#8 PEM private key or HMAC hexadecimal key string
JWS header
JWS payload
JWS signature string
https://www.rfc-editor.org/rfc/rfc7515.html
await signJWS("RS256", prvkey, "eyJOe..", "eyJpc...") -> "eyJOe..."
await signJWS("PS256", "-----BEGIN PRIVATE...", "eyJOe..", "eyJpc...") -> "eyJOe..."
await signJWS("ES256", "-----BEGIN PRIVATE...", "eyJOe..", "eyJpc...") -> "eyJOe..."
await signJWS("HS256", "12ab34...", "eyJOe..", "eyJpc...") -> "eyJOe..."
sign JWS (JSON Web Signature)