Implement extension importer.

Assets/Cryville/Crtr/Extensions/Extension.cs

@@ -1,10 +1,12 @@
 using Cryville.Crtr.Extension;
+using Cryville.Crtr.Extensions.Umg;
 using System.Collections.Generic;
 
-namespace Cryville.Crtr.Extensions.Umg {
+namespace Cryville.Crtr.Extensions {
 	public class Extension : ExtensionInterface {
 		public override IEnumerable<ResourceConverter> GetResourceConverters() {
 			return new ResourceConverter[] {
+				new ExtensionImporter(),
 				new ChartResourceImporter(),
 				new RulesetResourceImporter(),
 				new SkinResourceImporter(),

Assets/Cryville/Crtr/Extensions/ExtensionImporter.cs

@@ -0,0 +1,18 @@
+using Cryville.Crtr.Extension;
+using System.IO;
+
+namespace Cryville.Crtr.Extensions {
+	internal class ExtensionImporter : ResourceConverter {
+		static readonly string[] SUPPORTED_FORMATS = { ".dll" };
+		public override string[] GetSupportedFormats() {
+			return SUPPORTED_FORMATS;
+		}
+
+		public override void Convert(FileInfo file, ConversionSession ses) {
+			ses.AddResource(new ExtensionResource(file.Name, file));
+		}
+	}
+	public class ExtensionResource : FileResource {
+		public ExtensionResource(string name, FileInfo master) : base(name, master) { }
+	}
+}

Assets/Cryville/Crtr/Extensions/ExtensionImporter.cs.meta

@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: c048eb442e4b9304eb0637599be1084d
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: