The documentation here is great:
https://confluence.atlassian.com/bitbucket/publishing-a-website-on-bitbucket-cloud-221449776.html
However, I have a need that isn't covered here. I have some flat html files that are produced from a build process. I'd prefer to have the repo that builds it also be the repo that is used for the bitbucket.io "site". That would be possible, if the bitbucket.io web-root were configurable to be in a "web" (or other named) folder, rather than being required to be the repository root.
I don't want to expose all the processing files to the website. I only want the bitbucket.io "site" to have the flat HTML available to web users.