Updates to build notes

[truedat101]

The top level readme is great and handles a lot of mix of philosophy and architecture. For someone stumbling upon this and kicking the tires on porting/builds, need a few more details on different platform quirks.

• Linux has the most complicated story, two or three architectures in (risc-v, arm, x86), every backend graphics renderer possible, N number of different front end UI toolkits etc. Window managers may vary.
• Windows 10/11 - VS, VScode, Cmake, MING, etc.
• Mac M series, iOS, Vision OS
• android
• wasm?
• other stuff???

No way I can support more than the 3 platforms Windows/Linux/Mac+mobile , however it should be possible for someone to try the other platforms following the lead in documentation for tried and tested platforms.