Versioned Reference Documentation and/or notes on what version of `shiny` certain methods appear

[coatless]

It would be great to have a versioned specific reference section or notes on when a function was added.

For example, Shiny for R includes a static site serving documentation by version:

https://shiny.posit.co/r/reference/shiny/

Alternatively, there could be a note that is added similar to Pandas regarding new functionality, e.g.

https://pandas.pydata.org/docs/reference/api/pandas.core.window.rolling.Rolling.skew.html

Or both! 😄