Changes:
- Fix invalid json generated by image2card.sh (s/,/:/)
- Make sure that image conversion works when supplied images
are not JPG.
- Adjust comments based on the current documentation:
https://owntracks.org/booklet/features/card/#shell-script
base64 defaults to 76 colums (base64 (GNU coreutils) 8.13)
-w, --wrap=COLS
wrap encoded lines after COLS character (default 76). Use 0 to disable line wrapping
also added -r flag to the mosquitto_pub in the comments