add ECDH algorithm support for JWE

[ObeydKhan]

Hi,
Currently DIR and RSA-OAEP-256 algorithms are supported for encryption/decryption. I would like to contribute a solution using ECDH-ES and Contact KDF.

ECDH is generally faster and uses smaller keys for equivalent security strength than RSA, making it more efficient.

Overview:
Elliptic-curve Diffie–Hellman (ECDH) is a key agreement protocol that allows two parties, each having an elliptic-curve public–private key pair, to establish a shared secret over an insecure channel. This shared secret may be directly used as a key, or to derive another key. The key, or the derived key, can then be used to encrypt subsequent communications using a symmetric-key cipher.