const github.com/refraction-networking/utls/dicttls.SigScheme_ecdsa_secp521r1_sha512

one use

	github.com/refraction-networking/utls/dicttls (current package)
		signaturescheme.go#L16: 	SigScheme_ecdsa_secp521r1_sha512            uint16 = 0x0603