Account for pipes in completion of single unlabelled argument

[zth]

Another quality-of-life thing. Previously, this: someArray->Array.map(<com> would ignore the pipe and complete as the first argument to Array.map, which would be the array itself, rendering a [] suggestion. With this change we instead get a function template suggested, like v => {}.

Next level on this would be to track the path/name of Array.map and change the suggested variable name in the function template to something nicer than the generic v, like item.