docs(release-notes): separate new changes from ones carried-over - #2400

Changed pages include:

• index.html - view
• search/index.html - view
• plugins/index.html - view
• managed-spin/index.html - view
• contribute/index.html - view
• continuous-deployment/index.html - view
• 404.html - view
• contribute/approve-review/index.html - view
• continuous-deployment/spinnaker-user-guides/index.html - view
• continuous-deployment/armory-admin/index.html - view

There are more changes not included in the list