feat: Add outputList template function

[halostatue]

Resolves #4253

[halostatue]

This is mostly a proof of concept, but if the limitations list … | toStrings is acceptable, then I think we're OK. Otherwise, we'll need to essentially implement toStrings internally to outputList.

I’m also not particularly fond of the name. However, I have been able to run the template in #4253 successfully:

$ go run . execute-template \
  '{{- $opts := dict
        "show-help" true
        "ordered" true
        "no-limit" true
        "header" "Choose a movie poison"
        "options" (list "cyanide" "arsenic" "iocaine powder") 
  -}}{{ includeTemplate "multichoice.tmpl" $opts }}'
["arsenic","iocaine powder"]