img: move images into the img dir

Trying to cleanup the objects in the root directory so there is less
random stuff to sort through.

Signed-off-by: Brandon Philips <[email protected]>

Author: Brandon Philips

Makefile

@@ -11,7 +11,7 @@ DOC_FILES := \
 	serialization.md
 
 FIGURE_FILES := \
-	media-types.png
+	img/media-types.png
 
 default: help