Expose "latest" vs "stable" version of the gradio docs

[freddyaboulton]

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Is your feature request related to a problem? Please describe.
As a potential gradio developer, I would like to see the docs corresponding to the latest gradio pypi release ("stable") as opposed to the latest main branch ("latest"). It's possible that the main branch could have broken demos/typos in the docs that could discourage potential developers from using gradio.

Describe the solution you'd like
Let users choose between "latest" vs "stable" versions of the docs on the website. In the future we can let them choose docs corresponding to any version of gradio. We can expose this functionality in a drop-down as it's done here:

Additional context
Add any other context or screenshots about the feature request here.

[freddyaboulton]

Some notes after discussing with the team:

We're all in agreement about wanting to do this but we should have a detailed discussion to scope this out before diving head first.

From @pngwn :

There are a bunch of moving parts here, including the need to provision new infra. I'm also not 100% certain we should automatically track main at all, but rather deploy when we release a new version of gradio and create ephemeral envs for each PR. This can be achieved easily if we change some of our deployment specifics.

Agree that website deploys for each PR would be great. Now that we automatically create github tags for each release, it should be easier to create website deployments only for released version.