Add exclude for test folder in tsconfig.json (smithy-lang#496)

Author: trivikr

smithy-typescript-codegen/src/main/resources/software/amazon/smithy/typescript/codegen/tsconfig.json

@@ -7,5 +7,6 @@
     "removeComments": true,
     "resolveJsonModule": true,
     "rootDir": "src"
-  }
+  },
+  "exclude": ["test/"]
 }