Add --json output flag to brotab list

[pschmitt]

This adds a --json flag to brotab list.

The output format looks like this:

[{"id": "a.1.186","title": "Add --json output flag to brotab list by pschmitt · Pull Request #113 · balta2ar/brotab","url": "https://github.com/balta2ar/brotab/pull/113"}]

[jackmac92]

Was hoping I'd find an open issue/PR re: json output. I'd find it really useful
is this something you're interested in @balta2ar ?

edit: using this for now

brotab list |
  # Converts each line of tab delimited output to a JSON list
  awk -F'\t' '{
   printf "[";
    for(i=1; i<=NF; i++) {
      printf "%s\"%s\"", (i>1 ? "," : ""), $i
    }
   print "]"
  }' |
  # Creates an object to add labels
  jq -c '{ id: .[0], title: .[1], url: .[2] }'