The library is now available on Platformio ("M5 Stack 4Relay Library") and Arduino IDE Library Manager.
Can I use your 4-Relay picture to add in my Readme.md file on Github ? And/or add this link: https://shop.m5stack.com/collections/m5-unit/products/4-relay-unit ?
If you want, you can add my Github link to your Arduino Example section.

@rcoppens
ESPNow !

https://github.com/sfekilou/M5STACK_4RELAY

Library with these functions:

begin(TwoWire &wireport,int sdaPin, int sclPin,uint32_t frequency); //Initialize I2C port
uint16_t ReadState(); //read 0x10 & 0x11 registers
SyncMode(bool Sync); //sync or async LEDs
void AllOff(); //set all relays to OFF
void Write4Relay(int number,bool state); //set or unset the relay number