add some comments

client/components/anchorPositioningPolyfill.js

@@ -1,7 +1,14 @@
+/*
+This file basically checks support for Anchor Positioning API in the browser,
+and then loads the Oddbird polyfill if support is lacking. 
+*/
+
 let polyfillPromise;
 
+// look for `anchorName` in the computed styles
 const supportsAnchorPositioning = ()=>'anchorName' in document.documentElement.style;
 
+// wait for initial render
 const afterInitialRender = ()=>new Promise((resolve)=>{
 	requestAnimationFrame(()=>{
 		requestAnimationFrame(resolve);