Tested on https://electronics.semaf.at/MFRC522-i2c-Tiny-Breakout-Board
Set the Pin for the RST and i2c address!
#define RST_PIN 6 // Arduino UNO
// #define RST_PIN 14 // D5 on NodeMCU
// 0x28 is i2c address of the NFC Reader. Check your address with i2cscanner if not match.
MFRC522 mfrc522(0x28, RST_PIN); // Create MFRC522 instance.
Thanks to @arozcan for the MFRC522 i2c Library