Without this, going to `https://thelounge.example.com/index.html` would return the raw file. This now excludes it from the `public` folder so it cannot be rendered as is.
Renaming the file is for good measure, to indicate that this HTML file must be templated. Because it is a straight rename with no modification, rebasing PRs on it should not be to painful, as git re-applies changes on renamed files.
