feat: add override helper functions

These help us keep track of relevant metadata information about
overrides, so that we know what they are when we update a pack.

Signed-off-by: flow <flowlnlnln@gmail.com>

launcher/modplatform/helpers/OverrideUtils.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <QString>
+
+namespace Override {
+
+/** This creates a file in `parent_folder` that holds information about which
+ *  overrides are in `override_path`.
+ *
+ *  If there's already an existing such file, it will be ovewritten.
+ */
+void createOverrides(QString name, QString parent_folder, QString override_path);
+
+/** This reads an existing overrides archive, returning a list of overrides.
+ *
+ *  If there's no such file in `parent_folder`, it will return an empty list.
+ */
+QStringList readOverrides(QString name, QString parent_folder);
+
+}  // namespace Override