add member (#99)

Author: mkdev10

src/contents/index.md

@@ -29,4 +29,5 @@ AWS Amplify の利用方法、実運用含めた開発時の知見や課題、
 - Koya Kimura ([@koyakimura](https://twitter.com/koyakimura))
 - Ryotaro Tsuzuki ([@_unirt](https://twitter.com/_unirt))
 - Takahiro Suzuki ([@tkasuz](https://twitter.com/tkasuz))
-- Riku Inada ([@inada_riku](https://twitter.com/inada_riku))
+- Riku Inada ([@inada_riku](https://twitter.com/inada_riku))
+- Masachika Kuwabara ([@mkdev_10](https://twitter.com/mkdev_10))