fix: render now maps to lowercase DOM events (#507)

make events all lowercase, since our linter now enforces onClick instead of onclick

Author: seefeldb

typescript/packages/common-html/src/render.ts

@@ -248,7 +248,7 @@ const cleanEventProp = (key: string) => {
   if (!key.startsWith("on")) {
     return null;
   }
-  return key.slice(2);
+  return key.slice(2).toLowerCase();
 };
 
 /** Attach an event listener, returning a function to cancel the listener */