Mention cursor constraint explicitly.

An example is also added in screen-share#18

fixes screen-share#15

README.md

@@ -1,7 +1,7 @@
 # Screen-Capture Mouse Events
 
 Web applications can use `getDisplayMedia()` to capture any display-surface - tabs, windows or screens.
-When they do, they can also specify the cursor constraint to control whether the cursor's pixels are captured or not.
+When they do, they can also specify the [cursor constraint](https://www.w3.org/TR/screen-capture/#dfn-cursor) to control whether the cursor's pixels are captured or not.
 
 But what if the application wishes to programmatically observe the location of the cursor?
 That can be done by scanning each frame and employing heuristics to detect the cursor.

index.html

@@ -57,6 +57,8 @@ <h3>Use case #2: Efficiency enhancements during RTC</h3>
           is per-frame IPC overhead which multiplies with the max framerate.
         </p>
         <p>
+          The <a data-cite="screen-capture/#dfn-cursor">cursor constraint</a>
+          can be used to omit the cursor from the captured frames.
           If mouse coordinates were known to the encoding application, it could transmit these
           coordinates to the receiving application (on another device). The receiver could then
           redraw a cursor on the other side. (Note that, depending on the decoder, this is likely