Add a plan

TODO.md

@@ -1,4 +1,5 @@
 # Plans
 
+- [ ] Check that generate a palette of just 1, 2, 3 or 4 colors works.
 - [ ] If the extracted palette from an image results in colors where some of the colors are used just on a very few pixels, consider using a different color in the palette.
       Example image, where the blue color perhaps should have been something else: https://raw.githubusercontent.com/xyproto/png2svg/241a8a9d43e7ff974f0a41cad2416df606e7be2c/img/rainforest_4c.svg