Support JSON With Comments

[connorshea]

VS Code supports it, as does GitHub linguist.

A bit of JSON with comments, using the identifier json:

{ 
  // This is json
  "json": true
}

A bit of JSON with comments, using the identifier jsonc:

{ 
  // This is jsonc
  "json": true
}

Rouge doesn't recognize jsonc as a valid language.

[sormy]

Seems like done here: https://github.com/jneen/rouge/blob/master/lib/rouge/lexers/json_doc.rb

[jneen]

We could add jsonc as an alias for json_doc I suppose!

[asbjornu]

When the fenced code block uses the http language specifier and the Content-Type equals application/json, how do we switch from the default json lexer to the jsonc lexer for the contents in the HTTP body of the code block? Example:

```http
HTTP/1.1 200 OK
Content-Type: application/json

{
  // It would be nice if this comment was supported
  "foo": "bar"
}
```

[jneen]

@asbjornu If you wouldn't mind creating a new issue next time, it'd make it easier for us to reference. I've pushed what I think addresses the above in #1592.