fix(tabs): add tabindex

source/components/layout/tabs.mjs

@@ -149,6 +149,8 @@ const resizeObserverSymbol = Symbol("resizeObserver");
  * @example /examples/components/layout/tabs-simple Simple Tabs
  * @example /examples/components/layout/tabs-active Active Tabs
  * @example /examples/components/layout/tabs-removable Removable Tabs
+ * @example /examples/components/layout/tabs-with-icon Tabs with Icon
+ * @example /examples/components/layout/tabs-fetch Fetch Tab Content from URL
  *
  * @issue https://localhost.alvine.dev:8440/development/issues/closed/268.html
  * @issue https://localhost.alvine.dev:8440/development/issues/closed/271.html
@@ -1213,6 +1215,7 @@ function getTemplate() {
 	return `
         <template id="buttons">
             <button part="button"
+					tabindex="0"
                     data-monster-role="button"
                     data-monster-attributes="
                     class path:classes.button,