Add typescript headers

[Startouf]

When writing in typescript :

Could not find a declaration file for module 'theredoc'. '/Users/me/[project]/node_modules/theredoc/index.js' implicitly has an 'any' type.
Try npm i --save-dev @types/theredoc if it exists or add a new declaration (.d.ts) file containing declare module 'theredoc';ts(7016)