Write Release Notes for 10.2

Update the page Nuxeo Server Release Notes with 10.2 release notes:

• Update page title
• Add link to JIRA 10.2 release notes
• Update link to 10.2 upgrade docs (URL will have changed)
• No need to use the tag below on 10.2 items since everything will be new?

  {{since '10.2'}}
  

Update config.yml to mark 10.2 as the new version:

new_version: '10.2'