Enable Kotlin syntax highlighting

src/app/ide/language-map.ts

@@ -30,5 +30,7 @@ export const LanguageMap: { [extension: string]: string; } = {
     css: 'css',
     less: 'less',
     scss: 'scss',
-    sh: 'shell'
+    sh: 'shell',
+    kt: 'kotlin',
+    kts: 'kotlin'
 };