Add SFDC PF Panel Information to Handbook page

Why is this change being made?

This change is being made to provide greater context to the PathFactory fields within Salesforce and provide details explanation for the SDR/Sales team on how to leverage those fields in their daily workflow.

/mention https://gitlab.com/gitlab-com/marketing/marketing-operations/issues/1521

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for proposed change, per say-why-not-just-what