Insert a widget at a given index

Insert a input field to the Dynamic form, before
the specified index

#6406
Add @author and @since

Add @author and @since

#6406
Add @author, and @since

Add @author, and @since

#6406
Merge pull request #243 from A24Group/feature-agency-edit-timesheet-intervals-ui-6406

Insert a widget at a given index