[FIX] web_widget_numeric_step: always display on touch screens; avoid layout jumping otherwise

Before this patch:
- On a tablet, buttons wouldn't display (big screen; can't hover).
- On a PC, fields would make layout jumps while hovering.

@moduon MT-4472

web_widget_numeric_step/static/src/numeric_step.scss

@@ -0,0 +1,14 @@
+// Copyright 2023 Moduon Team S.L.
+// License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl.html)
+
+.widget_numeric_step {
+    // Hide the buttons until the user hovers if possible
+    @media (hover: hover) {
+        .btn_numeric_step {
+            visibility: hidden;
+        }
+    }
+    &:hover .btn_numeric_step {
+        visibility: visible;
+    }
+}