refac: banners dismissible by default

Co-Authored-By: Jun Siang Cheah <me@jscheah.me>

src/lib/components/admin/Settings/Banners.svelte

@@ -52,7 +52,7 @@
 									type: '',
 									title: '',
 									content: '',
-									dismissible: false,
+									dismissible: true,
 									timestamp: Math.floor(Date.now() / 1000)
 								}
 							];