dev: add zmk docker tutorial to readme

README.md

@@ -57,6 +57,35 @@ Lastly, you can replace the point array in [`footprints/phi-caps`](./footprints/
 - 2 oled 0.91 inch i2c (optional)
 - 2 batteries 3.7v (optional, requres cable otherwise)
 
+# Firmware
+## Using ZMK locally using docker
+For now, this is the tutorial to get the goosekb to work.
+```bash
+cd <path-to-goosekb>
+docker volume create --driver local -o o=bind -o type=none -o device="<absolute-path-to-goosekb>/config/" zmk-config  # enter absolute path
+git clone https://github.com/zmkfirmware/zmk.git firmware/zmk
+nix shell nixpkgs#devcontainer  # or install devcontainer otherwise
+devcontainer up --workspace-folder firmware/zmk
+docker ps -a    # get zmk container name
+docker exec -it <zmk-container-name> /bin/bash
+# now from within container
+cd /workspaces/zmk
+west init -l app/
+west update
+# actually build the firmware
+cd app
+rm -rf build/
+west build -p -d build/left -b seeeduino_xiao_ble -- -DSHIELD=goose_left -DZMK_CONFIG="/workspaces/zmk-config"
+west build -p -d build/right -b seeeduino_xiao_ble -- -DSHIELD=goose_right -DZMK_CONFIG="/workspaces/zmk-config"
+cp build/left/zephyr/zmk.uf2 build/left.uf2
+cp build/right/zephyr/zmk.uf2 build/right.uf2
+# connect mcu with pc
+# double press the reset button
+# the file explorer should now show a usb media
+# copy the corresponding .uf2 firmware to the usb media
+# it should now auto-eject and run the new firmware
+```
+
 # Thanks
 - to https://github.com/MvEerd/ergogen/tree/mveerd for ergogen
 - to https://flatfootfox.com/ergogen-introduction/ for teaching ergogen