feat: Add support for Component signature

[eshuva]

The CycloneDX Python library currently doesn't support the signature field on components, as defined in CycloneDX v1.4+. Would you consider adding it?
Thanks.

[jkowalleck]

relevant spec: https://cyclonedx.org/docs/1.4/json/#metadata_component_signature

[jkowalleck]

Hello @eshuva , thank you for the feature request regarding $.components.signature.

Is this something you consider working on?

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CycloneDX python library is maintained by volunteers, and drive by members of the CycloneDX community.

• see 📣 Call for contribution #633