Add warning about C-space on Mac

[KevinDCarlson]

Modern OS X seems to reserve C-space for toggling keyboard encodings. The VS Code plugin suggests C-c C-r as usually a reasonable replacement for C-c C-space, so I've suggested adding the same tip. I don't know enough about C-c C-r to know whether this is dangerous advice or needs more expansion, or whether it's worth trying to understand how to override the system's control of C-space entirely.

[wadler]

Thanks for the suggestion!

I use a Mac, and I've never encountered that particular problem.

Rather than enlarge the text with a sentence or two for each problem some user might encounter, I wonder if it is better to add a "troubleshooting" section with hints such as this one. What do you think?

[KevinDCarlson]

Yes, that seems fine. I’m confused about who exactly this affects as one reading of this post is that it ought to affect everyone. Possibly that was briefly true and now it only affects people with multiple keyboards enabled. In fact given that it doesn’t affect all Macs maybe this is fine to just let people Google. https://www.reddit.com/r/MacOSBeta/s/PhcqVbBc2f