Create build.php

Created build.php file
Added new php code to search for build file and if it doesn't find it, it shows the file not found error

front/php/templates/build.php

@@ -0,0 +1,8 @@
+<?php
+	$file = "/home/pi/pialert/front/buildtimestamp.txt";
+	if (file_exists($file)) {
+		echo date("Y-m-d", ((int)file_get_contents($file)));
+	} else {
+		echo "File not found";
+	}
+?>