A .d.ts file is a type file. E.g. it would contain things like export type Alphabet = 'A' | 'B' | 'C'.

The purpose of the compiler is to transpile .ts files into .js files, so I don't think producing a single .d.ts file would've been perceived as a necessary feature.

See this StackOverflow post: About "*.d.ts" in TypeScript

I think what you really want to do is to compile everything into a single .js file. I believe webpack is the correct tool to use in this case.