crypto needed for QUIC

[armanbilge]

H/t @ChristopherDavenport in Discord

Cypher Suites
TLS_AES_128_GCM_SHA256 - Mandatory
AES_256_GCM_SHA384
TLS_CHACHA20_POLY1305_SHA256

Digital Signatures
rsa_pkcs1_sha256 (for certificates)
rsa_pss_rsae_sha256 (for CertificateVerify and certificates)
ecdsa_secp256r1_sha256

key exchange
secp256r1 (NIST P-256) MUST
X25519

[bblfish]

That would be something to be added to the branch on which PR #48 is.

The first thing that would be needed are test cases: Documents that show valid signatures for a given text with a given public and private key, ideally official documents. Perhaps @ChristopherDavenport has some pointers, as he was interested in those signature types? The existing signing algorithms all have their tests taken from the Signing Http Messages spec