Issue #3496586 by grimreaper: Accessibility: submit icon only

Closes #3496586

templates/input/input--button.html.twig

@@ -31,7 +31,10 @@
     {% elseif icon and icon_position == 'after' %}
       <button{{ attributes.addClass(classes) }}>{{ label }}{{ icon }}</button>
     {% elseif icon and icon_position == 'icon_only' %}
-      <button{{ attributes.addClass(classes) }}>{{ icon }}</button>
+      <button{{ attributes.addClass(classes) }}>
+        <span class="visually-hidden">{{ label }}</span>
+        {{ icon }}
+      </button>
     {% else %}
       <button{{ attributes.addClass(classes) }}>{{ label }}</button>
     {% endif %}