Robert Seidt

Added Compatibility to ESP32 and ESP8266

1

On the ESP platform the SerialConfig enum is defined as an int32 instead of int16 as for the other platforms. So based on the idea of PR #16 from @mostafahk...

Added Compatibility to ESP32 ESP8266

2

Added compatibility for espressifs esp32 and esp8266 Based on the idea from [mostafahk](https://github.com/mostafahk) in [PR#70](https://github.com/arduino-libraries/ArduinoModbus/pull/70/commits) which seems kind of abandoned (last commit 2 years ago) As the serial configuration enum...