Create documentation for Hospice Care Index

Currently, no documentation exists for Hospice Care Index in the Help Center. There is information available from the release notes from Feb 2022, but we need a separate article to help support our clients. The documentation should also discuss that the HCI metrics that are available in our tool are Trella calculated from newer data and are not based on the same time period that is used by CMS Care compare site. Thus the Trella-calculated metrics should be used for directionality.