I had the same idea a long time ago, but only finally managed to set it up a week ago.
Separately from Discourse, the method I have personally used for a long time is the SingleFile browser extension. It saves the site you are currently viewing as a single HTML file, preserving it as closely as possible to what you see, so that you can read it offline. There are countless HTML files sleeping in my ~/Downloads folder.
Because information on the internet does not stay there forever, the most reliable way is to save what you currently see on your own computer exactly as it is.
I already have many HTML files saved, and many more will be added in the future, so I have been thinking about a feature that would let me bring these files into Discourse to view and manage them there.
If you are planning to add a feature to “scrap” or clip website content, it will end up overlapping quite a lot with what the SingleFile extension already does well.
It would be great if there were a way to integrate with SingleFile directly or to import HTML files.