Hide arrows for input

lib/devtools.js

@@ -30,6 +30,12 @@ customElements.define('developer-tooling', class extends HTMLElement {
           #change-port-show {
             display: none;
           }
+          /* hide up/down arrow for input type=number */
+          input::-webkit-outer-spin-button,
+          input::-webkit-inner-spin-button {
+            -webkit-appearance: none;
+            margin: 0;
+          }
 
           .hidden {
             display: none;