Hey :-)
Just to let you know the .ino source file gives a compilation error and prevents automated builds (required when M5Stack changes the partition scheme).
https://github.com/PartsandCircuits/M5Stack-WiFiScanner/blob/master/M5Stack-WiFiScanner.ino#L6
The problem is quickly solved by commenting out the #include "String.h" in M5Stack-WiFiScanner.ino