Update part-4.md
Update part-4.md

1) Fixing a typo in var Event = keystone.List('Event') - L in "List" should not be capitalized
2) Adding an action property to the form for the post request to be sent to the api
frontyard/keystone,matthewstyers/keystone,matthewstyers/keystone,Pop-Code/keystone,Pop-Code/keystone,matthewstyers/keystone,frontyard/keystone,frontyard/keystone