Added keychron notes to the knowledge base

knowledge base/keychron.md

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+# Keychron
+
+1. set the keyboard to _Windows mode_ using the side switch
+
+1. hold `Fn + X + L` for 4 seconds to set the function key row to _fn mode_
+
+1. ensure the `hid_apple` module is loaded
+
+   ```shell
+   sudo modprobe hid_apple
+
+   # load at boot
+   echo 'hid_apple' | sudo tee /etc/modules-load.d/keychron.conf
+   ```
+
+1. configure the keyboard's _fn mode_:
+
+   ```shell
+   echo 0 | sudo tee /sys/module/hid_apple/parameters/fnmode
+
+   # load at boot
+   echo 'options hid_apple fnmode=0' | sudo tee /etc/modprobe.d/keychron.conf
+   ```
+
+## Further readings
+
+- [K8 keyboard user manual]
+- [Keychron fn keys in Linux]
+- [Apple Keyboard] on the [Archlinux wiki]
+
+[apple keyboard]: https://wiki.archlinux.org/index.php/Apple_Keyboard
+[k8 keyboard user manual]: https://www.keychron.com/pages/k8-keyboard-user-manual
+[keychron fn keys in linux]: https://mikeshade.com/posts/keychron-linux-function-keys
+
+[archlinux wiki]: https://wiki.archlinux.org