init app with koa and typescript

[dantas15]

use existing tsconfig from #2

[dantas15]

• koa with graphql: https://github.com/graphql-community/koa-graphql

[dantas15]

• koa introduction: https://koajs.com/#introduction

[dantas15]

• koa examples: https://github.com/koajs/examples

[dantas15]

• path-mapping in typescript: https://blog.rocketseat.com.br/path-mapping-typescript/

[dantas15]

solved in 746a9a9