add: ES256 usage (#1003)

docs/usage.rst

@@ -72,6 +72,21 @@ EdDSA encoding and decoding require the ``cryptography`` module. See :ref:`insta
     >>> jwt.decode(encoded, public_key, algorithms=["EdDSA"])
     {'some': 'payload'}
 
+Encoding & Decoding Tokens with ES256 (ECDSA)
+-------------------------------------------
+
+ECDSA encoding and decoding require the ``cryptography`` module. See :ref:`installation_cryptography`.
+
+.. code-block:: pycon
+
+    >>> import jwt
+    >>> private_key = b"-----BEGIN EC PRIVATE KEY-----\nMHcCAQEEIHAhM7P6HG3LgkDvgvfDeaMA6uELj+jEKWsSeOpS/SfYoAoGCCqGSM49\nAwEHoUQDQgAEXHVxB7s5SR7I9cWwry/JkECIRekaCwG3uOLCYbw5gVzn4dRmwMyY\nUJFcQWuFSfECRK+uQOOXD0YSEucBq0p5tA==\n-----END EC PRIVATE KEY-----\n"
+    >>> public_key = b"-----BEGIN PUBLIC KEY-----\nMFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEXHVxB7s5SR7I9cWwry/JkECIReka\nCwG3uOLCYbw5gVzn4dRmwMyYUJFcQWuFSfECRK+uQOOXD0YSEucBq0p5tA==\n-----END PUBLIC KEY-----\n"
+    >>> encoded = jwt.encode({"some": "payload"}, private_key, algorithm="ES256")
+    >>> jwt.decode(encoded, public_key, algorithms=["ES256"])
+    {'some': 'payload'}
+
+
 Specifying Additional Headers
 -----------------------------