Add actual description.

Author: geerlingguy

_boards_cm/sentinel-core.md

@@ -8,3 +8,6 @@ github_issue: "https://github.com/geerlingguy/raspberry-pi-pcie-devices/issues/7
 link: https://sanctuary-systems.com/sentinel-core/
 videos: []
 ---
+The [Sentinel Core](https://sanctuary-systems.com/sentinel-core/) is a Mini ITX motherboard for the Raspberry Pi CM5 meant for Home Assistant installations using AMD GPU-powered AI inference for applications like [Home Assistant Voice](https://www.home-assistant.io/voice-pe/).
+
+I have an early prototype version, and the design is mostly similar to the official CM5 IO Board, but with ATX power input, and the M.2 slot removed in favor of a full x16 (x1 electrically) PCIe slot, suitable for full size PCI Express hardware.