Do you have to use Github? What about dropbox? Maybe you can set up security there to prevent direct downloading somehow. I already serve normal HTML files from Dropbox and it works fine. But I'm guessing for the free Dropbox account security options might be limited.
Here are many more file sharing sites you might try, so you can see if they support HTML and TW5.
The file sharing is divided into several parts: "File sharing", and "Storing text, readme files, documentation", and "Can edit after file creation", and "Blockchain storage", etc.