made a start on the image-core library's documentation

original commit: 0c1afebb5a9c163a383c6f4959ad86f065c6d408

collects/mrlib/scribblings/image-core.scrbl

@@ -0,0 +1,24 @@
+#lang scribble/doc
+@(require "common.ss")
+
+@title{Image Core}
+
+@defmodule[mrlib/image-core]
+
+This library is the core part of the @racketmodname[2htdp/image] library that DrRacket
+links into the namespace of all languages that it runs. This ensures that minimal
+support for these images are the same in all languages, specifically including
+support for printing the images and constructing the core data structures making
+up an image.
+
+@defproc[(render-image [image image?]
+                       [dc (is-a?/c dc<%>)]
+                       [dx number?]
+                       [dy number?])
+         void?]{
+  Draws @racket[image] in @racket[dc] at the position (@racket[dx],@racket[dy]).
+}
+               
+@defproc[(image? [v any/c]) boolean?]{
+ Recognizes the images that library handles.
+}