Restructure content in README.md

[wmamills]

The README is a bit log and rambling.

The README is also the main page for the doygen docs which make it one big page also.

Issues/Actions

• Library categogy data is good but should be in the intro to each section
• • move this content into per module files in doc/ and replace by a table in README.
• Contributing info does not need to be on the main page, make a page and link it from README
• Simply build instructions on the main page (README) and move the detailed instructions to a sub-page.
• • Example1: Most people that build for Zephyr will use the Zephyr integration and it will just work. Move the details for the other 5% off the main page.
• • Example2: Build for bare-metal, use an existung generic target on main page. Move instucions on make a new custom target to new page and suggest they carrry that def in their build system instead of pushing to libmetal.
• (Example2b: ceva CPU port is just generic. Make it easy to support a new CPU that is generic.)

[github-actions]

This issue has been marked as a stale issue because it has been open (more than) 45 days with no activity.