[json] Add support for JSON comments

[LukeSavefrogs]

Add support for JSON comments (from JSON 5 onwards). This is NOT a standard feature (it is NOT present in the original json module), but it would be a very welcomed addition to this polyfill.

{
    /* This is a block comment */
    "key": "value",
    "key2": "value2", // This is an inline comment
}