Lib: Add shadow option to Button component

src/lib/components/form/Button.svelte

@@ -33,6 +33,9 @@
 
     /** The PopupSettings to trigger on click. Only if "href" is undefined. */
     trigger_popup?: PopupSettings;
+
+    /** Should the button have a shadow? */
+    shadow?: boolean;
   }
 
   let {
@@ -44,6 +47,7 @@
     activate = false,
     activate_href = false,
     trigger_popup = { event: "click", target: "invalid" },
+    shadow = false,
     ...restProps
   }: ButtonProps = $props();
 </script>
@@ -57,7 +61,7 @@
         ? `variant-filled-${color}`
         : ''} {width} {activate ? 'btn-hover' : ''} {activate_href && is_at_path(href)
         ? 'btn-hover'
-        : ''}"
+        : ''} {shadow ? 'shadow' : ''}"
       draggable="false"
       {...restProps}>{@render children()}</button
     >
@@ -67,7 +71,7 @@
     type={submit ? "submit" : "button"}
     class="btn select-none px-2 py-2 {color ? `variant-filled-${color}` : ''} {width} {activate
       ? 'btn-hover'
-      : ''}"
+      : ''} {shadow ? 'shadow' : ''}"
     draggable="false"
     use:popup={trigger_popup}
     {...restProps}>{@render children()}</button