docs/library/bluetooth: Document all allowed args to UUID constructor.

Signed-off-by: Damien George <damien@micropython.org>

docs/library/bluetooth.rst

@@ -764,4 +764,5 @@ Constructor
     The **value** can be either:
 
     - A 16-bit integer. e.g. ``0x2908``.
+    - An object with the buffer protocol and that is 2, 4 or 16 bytes long, e.g. ``b'\x08\x29'``.
     - A 128-bit UUID string. e.g. ``'6E400001-B5A3-F393-E0A9-E50E24DCCA9E'``.