Expose merging SBOMs

Hello 👋 we are starting the work on [integrating cyclonedx](https://github.com/buildpacks/rfcs/blob/main/text/0095-sbom.md) in [buildpacks](https://buildpacks.io/). As a part of this work, we need to be able to merge cyclonedx SBOMs provided by various buildpacks involved in the build process through our go based binary called the [lifecycle](https://github.com/buildpacks/lifecycle). We were hoping for the behavior exposed by the cyclonedx CLI to be available via a go library. Would it be possible to add this as an enhancement?