Update index.md (#1973)
Update index.md (#1973)

Bolded the words "Note" for consistency
Simplified sentences and lists

Co-authored-by: Dave Dorbin <3a983b921291999521a653180c5b82ccd2c36700@google.com>
spinnaker/spinnaker.github.io,spinnaker/spinnaker.github.io,spinnaker/spinnaker.github.io