JSON viewer should add double-quotes around properties that need it.

[evert]

We're basically using JSON5 syntax, and while this is legal:

{
  foo: "bar"
}

If the key contains (for example) a space we should encode like this:

{
  "foo 1 2": "bar"
}

So we should add quotes if the key name would be illegal with the quotes. This also includes empty keys, e.g:

{
  "": "hello world, yes this is legal
}

Real world example: