docs: update playground link (#93)

Author: Himenon

README.md

@@ -8,7 +8,7 @@ Since the parameters extracted from OpenAPI can be used freely, it can be used f
 
 ## Playground
 
-- [Playground](https://openapi-typescript-code-generator-playground.netlify.app)
+- [Playground](https://openapi-typescript-code-generator.netlify.app/)
 
 ## Installation
 

docs/ja/README-ja.md

@@ -6,7 +6,7 @@ OpenAPI から抽出したパラメーターは自由に使うことができる
 
 ## Playground
 
-- [Playground](https://openapi-typescript-code-generator-playground.netlify.app)
+- [Playground](https://openapi-typescript-code-generator.netlify.app)
 
 ## DEMO