Add a note on the new folder for caching contour maps

generated_contour_maps/here are the cache contour maps generated.txt

@@ -0,0 +1,3 @@
+This folder contains the generated contour maps required for instance segmentation.
+Since generating them can be slow, I have them cached in this folder.
+Do note if you have made changes to the labels, you need to delete the corresponding contour map here to make the tool regenerate new ones.