Update release instructions README.md (#5482)
Update release instructions README.md (#5482)

* Update README.md

Fix json url typo
Clarify some points
Add readthedocs instructions
Rephrase
Incorporate feedback
Added Release model section

Lan-Hekary/Arduino,sticilface/Arduino,sticilface/Arduino,esp8266/Arduino,esp8266/Arduino,esp8266/Arduino,esp8266/Arduino,sticilface/Arduino,sticilface/Arduino,Lan-Hekary/Arduino,esp8266/Arduino,Lan-Hekary/Arduino,Lan-Hekary/Arduino,Lan-Hekary/Arduino,sticilface/Arduino