Added clip image to MicroPython pico_display docs

Updated the text and added clip.jpg to the MicroPython Pico Display docs to help communicate the use of clips.

micropython/modules/pico_display/README.md

@@ -176,12 +176,14 @@ picodisplay.text(string,x,y,wrap, scale)
 
 ### set_clip
 
-This function defines a rectangular area outside which no drawing actions will take effect.  If a drawing action crosses the boundary of the clip then only the pixels inside the clip will be drawn.  Note that `clip` does not remove pixels which have already been drawn, it only prevents new pixels being drawn outside the described area.  Only one clip can be active at a time, and defining a new clip replaces any previous clips.  The `x` and `y` parameters describe the upper-left corner of the clip area, `w` and `h` describe the width and height in pixels.
+This function defines a rectangular area outside which no drawing actions will take effect.  If a drawing action crosses the boundary of the clip then only the pixels inside the clip will be drawn.  Note that `clip` does not remove pixels which have already been drawn, it only prevents new pixels being drawn outside the described area.  A more visual description of the function of clips can be found below.  Only one clip can be active at a time, and defining a new clip replaces any previous clips.  The `x` and `y` parameters describe the upper-left corner of the clip area, `w` and `h` describe the width and height in pixels.
 
 ```python
 picodisplay.set_clip(x,y,w,h)
 ```
 
+![A diagram explaining clips](/micropython/modules/pico_display/clip.jpg)
+
 ### remove_clip
 
 This function removes any currently implemented clip.