feat: add support for RFC 7396 application/merge-patch+json (#1084)

Author: byted

openapi3filter/req_resp_decoder.go

@@ -1264,6 +1264,7 @@ func decodeBody(body io.Reader, header http.Header, schema *openapi3.SchemaRef,
 func init() {
 	RegisterBodyDecoder("application/json", JSONBodyDecoder)
 	RegisterBodyDecoder("application/json-patch+json", JSONBodyDecoder)
+	RegisterBodyDecoder("application/merge-patch+json", JSONBodyDecoder)
 	RegisterBodyDecoder("application/ld+json", JSONBodyDecoder)
 	RegisterBodyDecoder("application/hal+json", JSONBodyDecoder)
 	RegisterBodyDecoder("application/vnd.api+json", JSONBodyDecoder)