We've added the PluginEmbedded plugin on the site, and configured it to show the "html" subdirectory of project ssh account home areas. Thus you can upload html files there, (with a suitable "index.html") and if people go to the "HTML" tab of your project, they should see them.
In other words, for the "foo" project, you can
ssh email@example.com chmod a+x . ssh firstname.lastname@example.org mkdir html scp some-file.html email@example.com:html/index.html
Then in your Projects Settings/Modules tab, enable the "Embedded" module.
And then you should see that html content in your "HTML" tab of your project.
Note that currently only Managers of a project can login interactively and/or scp files into the project account home area.
Note also that your project won't have an ssh account unless you setup a "create_me" repository -- see CreatingRepositories