please add "readHeater" function

[Sisyphos0]

Hi,

Great Lib, thanks enjoyneering!

May I suggest addition of a "readHeater" function like this:

class HTU2xD_SHT2x_SI70xx {
public:
...
bool readHeaterEnabled(void);
...
};

bool HTU2xD_SHT2x_SI70xx::readHeaterEnabled(void){
uint8_t userRegData = _readRegister(HTU2XD_SHT2X_SI70XX_USER_READ_REG);
bool heaterEnabled = ((userRegData & HTU2XD_SHT2X_SI70XX_USER_CTRL_HEATER_ON)?true:false);
return heaterEnabled;
}

Tested with ESP32 & SHT20.