Write Release Notes for 11.1

Update the page Nuxeo Server Release Notes with 11.1 release notes:

• Update page title
• Add link to JIRA 11.1 release notes
• Update link to 11.1 upgrade docs (URL will have changed)
• No need to use the tag below on 11.1 items since everything will be new?

  {{since '11.1'}}
  

Update config.yml to mark 11.1 as the new version:

new_version: '11.1'