Extend config with various options from 1.x

Signed-off-by: Philip Molares <philip.molares@udo.edu>

src/config/utils.ts

@@ -0,0 +1,17 @@
+/*
+ * SPDX-FileCopyrightText: 2021 The HedgeDoc developers (see AUTHORS file)
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+export const toArrayConfig = (configValue: string, separator = ',') => {
+  if (!configValue) {
+    return [];
+  }
+
+  if (!configValue.includes(separator)) {
+    return [configValue.trim()];
+  }
+
+  return configValue.split(separator).map((arrayItem) => arrayItem.trim());
+};