[css-paint-api] Add defaults for some unexported HTML terms, so we don't have to wait for them to be exported.

Author: tabatkins

css-paint-api/Overview.bs

@@ -36,6 +36,9 @@ Ignored Terms: PaintWorklet
 <pre class="link-defaults">
 spec:infra; type:dfn; text:list
 spec:webidl; type:dfn; text:converting
+spec:html; type:dfn;
+    text:set bitmap dimensions;
+    text:reset the rendering context to its default state
 </pre>
 
 <pre class="anchors">