Add elliptic curve support for JWT signature

[GekySan]

Description

This pull request implements EC signing support for JWT encoding. The JwtEncode method has been modified to include support for ES256, ES384 and ES512 algorithms.

Type of change

• [x] New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• [X] Tests have been carried out to verify the encoding functionality for each ECDSA algorithm.

  Example in LoliCode :

string privateKey = @"-----BEGIN EC PRIVATE KEY-----
MHQCAQEEIEYgBlyQVsH7SpHUH7x4RErcckhu7ary/JjhP72Nk19EoAcGBSuBBAAK
oUQDQgAE1MtHIxlGP5TARqBccrddNm1FnYH1Fp+onETz5KbXPSeG5FGwKMUXGfAm
SZJq2gENULFewwymt+9bTXkjBZhh8A==
-----END EC PRIVATE KEY-----";

BLOCK:JwtEncode
  algorithm = ES256
  secret = @privateKey
  payload = "{\"open\":\"bullet\"}"
  => VAR @jwtEncodeOutput
ENDBLOCK

[openbullet]

Thanks again! Please next time ask to merge into the staging branch instead of master if you can, thanks 😉