Replaced hardcoded SourceType with custom defined ISourceResolver.

OpenRA.Mods.Common/Installer/ISourceResolver.cs

@@ -0,0 +1,19 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2022 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+namespace OpenRA.Mods.Common.Installer
+{
+	public interface ISourceResolver
+	{
+		string FindSourcePath(ModContent.ModSource modSource);
+		Availability GetAvailability();
+	}
+}