Missing "x5c" key for serialized ECKey and others.

[sallner]

Hello and thanks for the good work on this library.

While I was using it I came across one inconsistency with respect to handling x5c certificates on various asymmetric keys. It looks that in principle

JWTConnect-Python-CryptoJWT/src/cryptojwt/jwk/asym.py

Line 24 in 69b064b

JWK.__init__(self, kty, alg, use, kid, x5c, x5t, x5u, **kwargs)

will store the x5c on the key instance but only for RSAKeys this is also included in serialize().

JWTConnect-Python-CryptoJWT/src/cryptojwt/jwk/rsa.py

Lines 384 to 385 in 69b064b

	if self.x5c:
	res["x5c"] = [as_unicode(x) for x in self.x5c]

Is this intentional? In principal I see no problem, that also other asymmetric keys could have a x5c certificate attached to it, in particular the ECKey.
Would you consider this a reasonable change?

[jschlyter]

I believe it is reasonable to include x5c for all keys - please submit a PR (with tests)

[sallner]

Thanks for the positive feedback. I will try to sort out the CLA with my employer and come back to this ASAP.