[WIP] JSON5 is not supported by STJ

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original issue description:

Description

See https://json5.org

Reproduction Steps

Try to parse the kitchen sink example from json5.org:

{
  // comments
  unquoted: 'and you can quote me on that',
  singleQuotes: 'I can use "double quotes" here',
  lineBreaks: "Look, Mom! \
No \\n's!",
  hexadecimal: 0xdecaf,
  leadingDecimalPoint: .8675309, andTrailing: 8675309.,
  positiveSign: +1,
  trailingComma: 'in objects', andIn: ['arrays',],
  "backwardsCompatible": "with JSON",
}

Expected behavior

Parses fine.

Actual behavior

Fails

Regression?

No

Known Workarounds

No response

Configuration

No response

Other information

No response

Original prompt

---

This section details on the original issue you should resolve

<issue_title>JSON5 is not supported by STJ</issue_title>
<issue_description>### Description

See https://json5.org

Reproduction Steps

Try to parse the kitchen sink example from json5.org:

{
  // comments
  unquoted: 'and you can quote me on that',
  singleQuotes: 'I can use "double quotes" here',
  lineBreaks: "Look, Mom! \
No \\n's!",
  hexadecimal: 0xdecaf,
  leadingDecimalPoint: .8675309, andTrailing: 8675309.,
  positiveSign: +1,
  trailingComma: 'in objects', andIn: ['arrays',],
  "backwardsCompatible": "with JSON",
}

Expected behavior

Parses fine.

Actual behavior

Fails

Regression?

No

Known Workarounds

No response

Configuration

No response

Other information

No response

<agent_instructions>Create a separate implementation at the lowest possible level allowed by STJ extensibility. The new implementation must NOT reply on any APIs that are not public, since we might need to ship this as a separate nuget package.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

Fixes #1

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[kzu]

where's the work @copilot ?