copy local images referenced from ![]() from content to dist

[Guria]

Markdown file images should work on github while browsing content dir.
Built html files should have working links inside dist folder.

[awinogradov]

👍

[Guria]

I have work arounded it in my setup Guria/cerebral-website@c422ff0...759605d

But feature from the box would be great :)

[awinogradov]

@Guria I know you can create super PR ;)

[Guria]

I can when will have a time for it