document onscreen keyboard setup in README.md

[GorgiAstro]

This merge request contains no code, it only documents how to set up the onboard virtual keyboard to be used in Mixxx.

Actions required:

• Can someone else test it on Raspberry Pi OS?
• Can someone test it on Ubuntu? Some instructions maybe only work for Raspberry Pi OS
• Where is the best place for this documentation? It takes a lot of space in README.md.

[timewasternl]

I'm thinking of creating a folder called "extras" or "integrations" for such things, as they will contain optional integrations. In there, we can create separate markdown files per feature.
In there, we can also link the project by @bencejuhaasz (https://github.com/bencejuhaasz/Pioneered-Plus) for deeper integration with the controller mapping for the DDJ-400.

I will test the instructions later today.

[bvobart]

Where is the best place for this documentation?

I'm thinking of creating a folder called "extras" or "integrations" for such things, as they will contain optional integrations. In there, we can create separate markdown files per feature.

Hmmm, don't think that'd be nice in this repo for people who just want to download the skin, might be better to do it in a separate repo such as Pioneered Plus or maybe on a Wiki on this repo, if you enable that in the repo's settings.

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Nice guide though, clear and beginner-friendly with helpful pictures :) It is very Raspberry Pi OS specific, yes. The installation command probably works on Ubuntu too (on Manjaro ARM -- which is what I run on my own RPi -- it's sudo pacman -S onboard), but the UI and where to add it to the startup apps could be completely different for anything else than the Pi OS' PiXeL desktop environment.

[timewasternl]

[...]or maybe on a Wiki on this repo, if you enable that in the repo's settings.

Great idea, totally forgot about this feature.
I have enabled it and added you all as contributor :)

@GorgiAstro, would you like to take the honour of putting your documentation on the first Wiki page?