#820 clarification on the meaning of the max and min properties for s…

…parse accessors

specification/2.0/README.md

@@ -500,6 +500,7 @@ The following fragment shows an example of `sparse` accessor with 10 attributes
 }
 ```
 A sparse accessor differs from a regular one in that `bufferView` and `byteOffset` properties aren't required. When these properties are omitted, the sparse accessor is initialized as an array of zeros of size `(size of the accessor attribute type) * (accessor count)` bytes.
+A sparse accessor `min` and `max` properties correspond, respectively, to the minimum and maximum component values once the sparse substitution is applied.
 
 #### BufferView and Accessor Byte Alignment