[WIP] Add details on signing method to signature documentation

[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 prompt

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This section details on the original issue you should resolve

<issue_title>Signature is lacking details on signing method</issue_title>
<issue_description>"Signature" is lacking details on signing method.

Please provide details on the signing method and cryptographic keys used to generate this signature.

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Document Details

⚠ Do not edit this section. It is required for docs.microsoft.com ➟ GitHub issue linking.

• ID: 1d758b4f-a129-68a6-5b1f-00a640924202
• Version Independent ID: 92531220-57ac-7602-e2b8-ed1d20d8298d
• Content: HardwareToken.Signature Property (Windows.System.Profile) - Windows UWP applications
• Content Source: winrt-api-build/xml/Windows.System.Profile/HardwareToken.xml
• Product: uwp
• Technology: winrt-reference
• GitHub Login: @hickeys
• Microsoft Alias: hickeys</issue_description>

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

• Fixes Signature is lacking details on signing method #1700

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