Switch to trailing comma style in spec/mocha.js

[dpilafian]

For multiline arrays and objects, the consistency of including a comma for the last item makes the code easier to edit and helps reduce merge diffs.

See:
https://jshint.com/docs/options/#trailingcomma

For example, change:

const input = {
   '$':  'Money',
   '🚀': 'Unicode'  //no comma
   };

to:

const input = {
   '$':  'Money',
   '🚀': 'Unicode',  //with comma
   };

[dpilafian]

I should have been more clear in the original description. The trailing commas are to be applied to the coding style of the spec/mocha.js file itself.

For example, the input object on line 51 needs a trailing comma:
https://github.com/center-key/pretty-print-json/blob/master/spec/mocha.js#L51

Changing the output to include trailing commas would, unfortunately, break JSON.

"JSON, however, disallows trailing commas."

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Trailing_commas

[AlcidesA]

Oh right, I'm gonna fix that

[dpilafian]

PR #27 looks good.

By the way, the new fancy JSON5 supports trailing commas. The future is getting brighter.