add placeholderView component

src/View/Components/placeholderView.tsx

@@ -0,0 +1,9 @@
+import * as React from "bloatless-react";
+
+export function PlaceholderView(text: string) {
+    return (
+        <div class="width-100 height-100 flex-column justify-center align-center">
+            <span class="secondary slide-up">{text}</span>
+        </div>
+    );
+}