apriltag porting for esp-idf

This repo demonstrates how to use apriltag in esp-idf.
maim/convert.py can convert png image to grayscale image in uint8 formate, store as c array in pic.c.
maim/apriltag.c will find all apriltag in this image. It has been tested on esp32c3, esp32s3, but other esp32 family should also work.