BlueOS: Getting Started: Mention hotspot option

[ES-Alexander]

BlueOS 1.1 creates a hotspot that can be connected to if no other network connection is made on startup. This can be helpful for people connecting to BlueOS without an ethernet connection, like for use on a boat.

This is already documented in Advanced Usage, but should at least be mentioned in Getting Started as well. This will likely require re-ordering the Network Configuration section to only apply when connecting via ethernet, or if you want to pass through telemetry / connect to a GCS.

Should maybe be done together with bluerobotics/BlueOS-docs#7, but not essential.