add documentation to ecdsa constructor

Author: sandro97git

include/jwt-cpp/jwt.h

@@ -1570,6 +1570,14 @@ namespace jwt {
 					throw error::ecdsa_exception(error::ecdsa_error::invalid_key_size);
 			}
 
+			/**
+			 * Construct new ecdsa algorithm
+			 *
+			 * \param key_pair openssl EVP_PKEY structure containing ECDSA key pair. The private part is optional.
+			 * \param md Pointer to hash function
+			 * \param name Name of the algorithm
+			 * \param siglen The bit length of the signature
+			 */
 			ecdsa(helper::evp_pkey_handle key_pair, const EVP_MD* (*md)(), std::string name, size_t siglen)
 				: pkey(std::move(key_pair)), md(md), alg_name(std::move(name)), signature_length(siglen) {
 				if (!pkey) {