TSConfig

Offers a way to configure the root directory for where declaration files are emitted.

example
├── index.ts
├── package.json
└── tsconfig.json

with this tsconfig.json:

{
  "compilerOptions": {
    "declaration": true,
    "declarationDir": "./types"
  }
}

Would place the d.ts for the index.ts in a types folder:

example
├── index.js
├── index.ts
├── package.json
├── tsconfig.json
└── types
    └── index.d.ts