Add versioned docs or a visible version indicator to the docs

### Describe the Bug

Is it possible to have the docs versioned? If this is not feasible or preferred, it would be helpful if the version number is visible somewhere, even if it is always going to point to the latest stable version.

An anecdote to provide additional context, I used `--min-severity warn` but got a zero exit code. However, as per the [docs](https://pyrefly.org/en/docs/configuration/#min-severity), I expected it to work on the latest stable version on PyPi, which is `1.0.0`
> for example, --min-severity warn makes warnings cause a nonzero exit.

But it didn't, looking into issues here, it seems this is a feature for `1.1.0` as per the milestone in https://github.com/facebook/pyrefly/issues/3370. This confusion could be avoided if there were versioned docs or a version number.

Thanks :)

For reference, this is what other type checker docs do
[mypy](https://mypy.readthedocs.io/en/stable/index.html) - side bar has a version and there is a switcher for stable and latest.
[ty](https://docs.astral.sh/ty/) - latest tag is displayed, no version switcher
[zuban](https://docs.zubanls.com/en/latest/) - version switcher (though it only supports latest at the moment)
[pyright](https://microsoft.github.io/pyright) - None 🙃 (mentioned this just for fairness)

PS: I noticed an "INFO" box that mentions when a particular feature was implemented ([example](https://pyrefly.org/en/docs/configuration/#preset-all)). One could argue doing that would solve this specific issue, but I will let the maintainers decide that.

### Sandbox Link

_No response_

### (Only applicable for extension issues) IDE Information

_No response_