"latest" docs don't make it clear that they contain unreleased features

[kandersolar]

Is your feature request related to a problem? Please describe.
Someone on stackoverflow tried using the example code in our latest docs with pvlib 0.8.1 because they didn't realize the feature wasn't in a stable release yet: https://stackoverflow.com/questions/68357949/cant-find-pvlib-pvsystem-array

Describe the solution you'd like
A warning banner at the top of the pages at https://pvlib-python.readthedocs.io/en/latest/ saying something like "this page might use unreleased features; click here to view documentation for the current pvlib release". One straightforward method described here looks like this:

Describe alternatives you've considered

• Maybe just disable the "latest" docs altogether? If it's for unreleased features then what's the value in making it public?
• Another option, not sure it's maintained though: https://github.com/humitos/sphinx-version-warning

[AdamRJensen]

Recently, I have been finding myself often referring to new functions in the latest release, e.g., sending links to people. So I definitely think it has some usage. It's nice being able to somewhere see the current GitHub version, which I guess what 'latest' is.

As long as it defaults to 'stable', then I don't see an issue also having 'latest'. Clearly, whoever posted the question must have been peeking around the documentation in order to find the 'latest'.

I'm +1 for the banner solution!

[wholmgren]

+1 for the banner, but after 0.9.