Create BLE-based "Dongle Mode" Documentation

[jjhaefner]

While basic support was added in this PR, documentation on how one would actually configure dongle mode has not been created.

Goals of issue:

• Create home for dongle mode implementation with initial guide on configuration.
• Call out any pitfalls or missing features due to this being a new-ish capability, and that it isn't as easy as it could be.
• Make sure related issues are created/linked to documentation, and that those issues call out that the documentation should be updated alongside development.

[ryanwwest]

I'm very interested in this. Here are some questions that perhaps the documentation could also cover.

I'm wondering if using a third nicenano in 'dongle' mode would eliminate many of the problems I typically face with Bluetooth not immediately connecting, given that the connection is still BLE but the split keyboards are only paired to 'one' device.

I'm also wondering if there are any very small boards like https://tomu.im/ that could run ZMK when connected via USB to the computer. I understand nicenano can, but that is big enough that you couldn't leave it plugged into a laptop port indefinitely when traveling around.

[caksoylar]

I think it might make sense to consider this together with #948. Especially if we want there to be a "feature" page rather than a subsection under Development.

[Silverdev2482]

Not sure if this is the best place to ask, but I can't find a better one. I heard you can make a board into a dongle simply by making it the central part of a keyboard, I assume "dongle mode" is not this? Because I would like the keyboard to work normal with bluetooth if the dongle isn't powered or found.

[caksoylar]

Discord would be the better place to ask, since you already asked (and I replied there). You cannot dynamically switch a device between connecting to a ZMK dongle (which is the "central" part of a split keyboard) and connecting to other devices directly.