Allow program to be passed into generateDtsBundle

[Danielku15]

Currently dts-bundle-generator always creates a new TypeScript compilation using the provided compiler options.

https://github.com/timocov/dts-bundle-generator/blob/964f6c62d9f825d222661c179adc47fb7f23c6ac/src/bundle-generator.ts#L142C17-L146

I'd like to pass a custom ts.Program into generateDtsBundle

Use Case:

I want to create bundled DTS files inside a Rollup/Vite plugin. There I already have access to the ts.Program which is used to generally compile and bundle my library.

I create multiple d.ts for different entry points and this is currently very expensive. Reusing the existing program would help a lot speeding up the compilation.