Update Apps: Describe at documentation

[koppor]

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

Sometimes, tools release new versions. It should be possible to update installed tools

At https://www.jbang.dev/documentation/guide/latest/install.html, only installation is described, not updates.

Describe the solution you'd like

A clear and concise description of how to update an app installed via jbang app install.