Add bluetooth troubleshooting page

[TraceyC77]

Add page under troubleshooting about bluetooth devices not showing / connecting
A couple of users have had issues lately.

• If Xfce (other DEs using blueman?), make sure "Hide unnamed devices" is not checked
• Blueman troubleshooting page

General notes

Make sure the device is seen by your system.

To make sure your Bluetooth controller is seen by your system, run this command:

bluetoothctl list

Example output

$ bluetoothctl list
[NEW] Controller 00:02:72:C5:BB:B4 infirit [default]
[NEW] Device 6C:83:36:B9:C6:D6 Galaxy Nexus

If there are no controllers listed you either have,

A hardware killswitch enabled, usually called "airplane mode". Some laptops may have a physical switch for bluetooth, but this is uncommon.
An adapter that is not supported by the Linux bluetooth stack.

To check the later, you can find the hardware ID with lsusb or lspci depending on the interface to google for it.

Other useful docs to use as reference

Baeldung tutorial

Particularly
4. Connect a Bluetooth Device Using the Terminal