docs: bump install version in README to 0.2.1

Author: kikuomax

README.ja.md

@@ -21,7 +21,7 @@
 このレポジトリを依存関係(`dependencies`)に追加してください。
 
 ```sh
-npm install https://github.com/codemonger-io/cdk-rest-api-with-spec.git#v0.2.0
+npm install https://github.com/codemonger-io/cdk-rest-api-with-spec.git#v0.2.1
 ```
 
 このライブラリはCDK v2プロジェクトで使用することを想定しており、以下のモジュールは`dependencies`ではなく`peerDependencies`に含んでいます。

README.md

@@ -21,7 +21,7 @@ This library is implemented for the CDK **version 2** (CDK v2) and does not work
 Please add this repository to your dependencies.
 
 ```sh
-npm install https://github.com/codemonger-io/cdk-rest-api-with-spec.git#v0.2.0
+npm install https://github.com/codemonger-io/cdk-rest-api-with-spec.git#v0.2.1
 ```
 
 This library is supposed to be used in a CDK v2 project, so it does not include the following modules in the `dependencies` but does in the `peerDependencies`.