docs: rework README

[casperdcl]

• update sections
  • create, simplify & unify installation/setup into just 2 sections (basic at top & advanced at bottom)
  • more intuitive section names
• document cml-pr
• mark all "see also" examples which require PATs

---

• fixes overhaul README #557

follow-up (after this PR) #652

• replace #cml-functions table with auto-generated collapsed command --help (Improve docs explaining commands possible inputs #361)
• talk about runners after Cml runner long job #583
  • transparent spot instances
  • avoid timeouts limitations
• maybe more reordering à la docs: rework README #617 (comment)
• review PAT necessity How necessary is it to use a Personal Access Token? #625

[DavidGOrtega]

Personally I still see some flaws being the most delicate the Advanced section. Too much stuff there including Installation that should not be advanced at all 😁

Section CML reports before Getting started is a non sense to me. It does not mention cml-github-send-check either.

My logic structure

CML presentation and areas of development defining the three legs that CML has:

• metrics integration (tb and many to come)
• reports
• cloud provision

metrics integration (tb and many to come)

collapsible Gitlab or wiki link
collapsible GH or wiki link
collapsible BB or wiki link

reports

collapsible Gitlab or wiki link
collapsible GH or wiki link
collapsible BB or wiki link

cloud provision

collapsible Gitlab or wiki link
collapsible GH or wiki link

Installation

env variables

Command Reference

[DavidGOrtega]

Great! 🙏