Make it possible to generate only given template files

#### Reason/Context
I'd like to use generator not only to scaffold my project when I start working on my application. I also want to use it continuously, every time I change something in AsyncAPI document.

The problem is that regeneration means basically another generation of the entire template. This leads to a process of regenerate -> carefully go through each change introduced after regenerating and ignore changes that will break your code

More context [here](https://deploy-preview-237--asyncapi-website.netlify.app/blog/websocket-part3#keeping-asyncapi-in-sync-with-code).

#### Description

A partial solution for the problem, but also not very complicated would be a configuration I could pass to the library/cli where I could specify what files to include/exclude in a generation.

Let's say I use some Node.js template. I generated my app and later added some more dependencies for my business login. Later I want to regenerate, but by telling the generator to ignore **package.json** and **package-lock.json** files.

What do you think? is the use case clear? you think it makes sense?

Start with the generator's library/CLI configuration entry point and the Node.js template behavior described in the issue. Use package.json and package-lock.json as the example files, then verify that an include/exclude configuration regenerates selected files while leaving excluded files unchanged.

Written by the indexing model from the issue text.