Fixes #518: Add Cytron CM4 Maker Board.

Author: geerlingguy

_boards_cm/cytron-cm4-maker-board.md

@@ -0,0 +1,12 @@
+---
+layout: board
+title: "Cytron CM4 Maker Board"
+short_description: A board for makers with an NVMe 2242 slot and plenty of GPIO and Grove and Stemma QT ports.
+status: production
+picture: "/images/board-cytron-cm4-maker-board.jpg"
+github_issue: "https://github.com/geerlingguy/raspberry-pi-pcie-devices/issues/518"
+link: https://www.cytron.io/c-raspberry-pi/c-raspberry-pi-main-board/c-raspberry-pi-cm/p-cm4-maker-board-and-kits
+videos:
+  - https://www.youtube.com/watch?v=xp7JqUJgsXQ
+---
+Cytron's [CM4 Maker Board](https://www.cytron.io/c-raspberry-pi/c-raspberry-pi-main-board/c-raspberry-pi-cm/p-cm4-maker-board-and-kits) is a carrier board meant for testing and experimentation. It has a full-size GPIO header with LEDs for certain GPIO pin status, buttons attached to other GPIO, Grove and Stemma QT connectors for prototyping, an RTC and buzzer, Audio output, and a 2242 M.2 NVMe slot.