Add information on releasing Bevy games

For relative newcomers to Rust, we should start a section on Releasing Bevy games, to go along with our advice on fast compilations.

This should include:
- maximizing the optimization level (#4586)
- using relative rather than absolute paths
- how to build executables for different platforms
- eventually, links to concrete advice on releasing the game on various distribution platforms like Steam and itch.io

This information likely deserves its own page, but should be linked on the Bevy website, perhaps near the section on fast compilation.