improve cross-OS description of where to look for new USB devices

[lesshonor]

Original discussion: https://github.com/btgrant-76/MW-BDE-r2-guide/pull/1#discussion_r923388694

• The current table isn't great, especially on mobile:
  
• @btgrant-76 has pointed out an alternative method of checking for macOS. I can't verify that the current method is correct, and if it isn't the other method described definitely doesn't fit well into the table.
• The Linux method requires superuser and doesn't act the same way as the others (...it's just the kernel ring buffer). Find something nicer.

[lesshonor]

So, after discovering <details> while writing MurphPad's ZMK readme, I immediately began thinking of an approach like this:

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Where to look on Windows

**Settings > Bluetooth and other devices:** 

Where to look on macOS

**About this Mac > System Report... > Hardware/USB > USB Device Tree** 

Where to look on Linux

**Wherever Ubuntu handles this** - [ ] spin up Ubuntu LiveUSB, plug PM in, take screenshot If the above isn't an option for you, `sudo dmesg` will display the kernel ring buffer; the last device plugged in will be near the bottom.  (Some kernels have `dmesg -w`, which will tail `dmesg` so you can plug the PM in after running the command.)

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...I would, rather obviously, require assistance with an approach of this nature.