Add a section for 'Platforms'.

[MikeCodesDotNET]

I think it might be a good idea to change the current 'Deployment / Publishing' section to 'Platforms', which then sub-sections for each supported platform. We can then have the deployment docs and other platform-specific info within these sub-sections.

I imagine a structure something like:

• Platforms
  • Windows
    • Publishing / Deployment
      • Ad-Hoc
      • Microsoft Store
    • Supported Versions
  • macOS
    • Publishing / Deployment
      • Ad-Hoc
      • App Store
    • Supported Versions
  • Linux
    • Publishing / Deployment
    • Supported Distros