JSON Comments support

[neuecc]

JSON Comments is invalid JSON Format but used widely(for example, VSCode - settings.json) and also supports JSON.NET. Utf8Json suports both single-line comment and multi-line comment.

{
    // allow single line comment
    "foo": true, // trailing
    /*
      allow
      multi
      line
      comment
    */
    "bar": 999 /* trailing */
}

commit:
5e42348

[neuecc]

v1.3.0 includes this improvement.