Menu Item Custom Action elements.xml

<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
  <CustomAction Id="21c1f1f7-70ad-4a02-92e1-444cb991c251.App-MenuItemCustomAction"
                RegistrationType="List"
                RegistrationId="100"
                Location="EditControlBlock"
                Sequence="10001"
                Title="My App Part">
    <!-- 
    Update the Url below to the page you want the custom action to use.
    Start the URL with the token ~remoteAppUrl if the page is in the
    associated web project, use ~appWebUrl if page is in the app project.
    -->
    <UrlAction Url="~appWebUrl/Pages/Default.aspx" />
  </CustomAction>
</Elements>