[css-paint-api] Fix issue.

Author: bfgeek

css-paint-api/Overview.bs

@@ -176,10 +176,10 @@ The <<paint()>> function is an additional notation to be supported by the <<imag
 For the 'cursor' property, the <<paint()>> function should be treated as an <a>invalid image</a> and
 fallback to the next supported <<image>>.
 
-Issue(w3c/css-houdini-drafts): Support additional arbitrary arguments for the paint function. This
-    is difficult to specify, as you need to define a sane grammar. A better way would be to expose a
-    token stream which you can parse into Typed OM objects. This would allow a full arbitrary set of
-    function arguments, and be future proof.
+Issue(w3c/css-houdini-drafts#100): Support additional arbitrary arguments for the paint function.
+    This is difficult to specify, as you need to define a sane grammar. A better way would be to
+    expose a token stream which you can parse into Typed OM objects. This would allow a full
+    arbitrary set of function arguments, and be future proof.
 
 The 2D rendering context {#2d-rendering-context}
 ================================================