JSON5 Marshaling

[BigBoyBarney]

Hi!

The way JSON marshaling / unmarshaling works is fantastic, and I find it super cool that JSON5 is supported at all. Thank you for that!!

Currently, even if the marshal options specify JSON5, it will output plain JSON. This is technically not wrong, as plain JSON is valid JSON5, but sort of defeats the purpose of it.

Example use case: I would like to use JSON5 for a project's config file, to make it more user-friendly and less ugly. Parsing the file is no problem, but saving the config again will un-json5 the config file, which means a template engine would be needed.

Currently, json.Marshal_Options has a few fields to control how MSJON is marshalled, maybe something similar could be done for JSON5, to make it output the superset instead of plain?

---

Thanks in advance!