feat: use input element directly

Previously, a button proxy was used which required the use of complicated reference management. Using the HTML `input` element directly simplifies the implementation.

Also moved some styles.

ref: N25B-189

src/index.css

@@ -26,7 +26,6 @@ html, body, #root {
 }
 
 a {
-  font-weight: 500;
   color: canvastext;
 }