Allow the use of any branch for stable

[zedzhen]

I want to be able to change the documentation, without releasing a new release.
I found the article https://til.simonwillison.net/readthedocs/stable-docs.
However, for it to work, it is necessary that the branch be called "stable". I would like to name it "docs/stable" (as there will be branches for each major release of "docs/v*")
Now, when trying to use the "stable" url for another branch, it causes the error "A version with that slug already exists.". However, stable is not active.

[humitos]

Yeah, stable slug is special on Read the Docs. You cannot use that slug for another version. This is a current limitation.