Improved settings of CSPs.

Added manifest.json.
Added further security-related HTTP headers.

manifest.php

@@ -0,0 +1,40 @@
+<?PHP
+/**
+ * This file generates a web manifest based on the settings.
+ *
+ * @author Joshua Ramon Enslin <joshua@jrenslin.de>
+ */
+
+// Include functions and settings.
+
+require_once __DIR__ . "/inc/functions.php";
+
+// Ensure working environment for frontend.
+
+ensureEnvironment();
+
+// Fill output array
+
+$data = [];
+
+$data["name"] = $data['short_name'] = $settings['pageTitle'];
+$data["start_url"] = "/";
+$data["display"] = "standalone";
+$data["background_color"] = "#000";
+$data["theme_color"] = "#AFB42B";
+$data["description"] = "Website of " . $settings['pageTitle'];
+
+/*
+$data['icons'] = [
+    "src"  => $settings['logo'],
+    "type" => mime_content_type(__DIR__ . $settings['logo'])
+];
+ */
+
+// Return JSON-encoded data.
+
+header('Content-Type: application/json');
+echo json_encode($data, JSON_PRETTY_PRINT);
+
+?>
+