Kibana and solutions release notes best practices for devs

[florent-leborgne]

Turning the generated release notes output into a qualitative document requires too much effort as of today.
One of the key cause is PRs themselves that in the vast majority of cases:

• are incorrectly labeled (severity and product category)
• have an unclear title or are missing a release notes section that focuses on user-related changes

This issue is for creating simple yet comprehensive guidelines to explain more clearly:

• how release notes are generated
• what are the best practices to ensure better unedited quality

[florent-leborgne]

Considering the page done for now. I'll think of some actions to put this in front of engineers when I'm back.