Add language and release selectors to web hosted user documentation

[seanbudd]

Is your feature request related to a problem? Please describe.

Each release post we link to the changes file hosted at: https://www.nvaccess.org/files/nvda/releases/2024.3/documentation/en/changes.html.

The user guide is also hosted at a similar URL https://www.nvaccess.org/files/nvda/releases/2024.3/documentation/en/userGuide.html.

We also host translated documentation, but the UX to reach it is quite obscure, e.g. through file browsing at:

https://www.nvaccess.org/files/nvda/releases/2024.3/documentation/

Describe the solution you'd like

It would be nice to have drop-down selectors to select language and release while browsing a user guide or changes doc.

Describe alternatives you've considered

Existing navigation e.g. https://www.nvaccess.org/files/nvda/releases/2024.3/documentation/

Additional context