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README.md

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+Lightweight Docker images for [ZMK][zmk].
+
+### Platforms
+
+- `arm`
+
+### Images
+
+#### build
+
+For _building_ [ZMK][zmk] firmware with CI.
+
+- FROM: **[debian][debian]:stable-slim**
+- Includes:
+  - essential [Zephyr][zephyr] dependencies (`apt-get`)
+    - non-build dependencies are _not_ included. e.g. `pip3`, UI packages, etc.
+  - base [Zephyr][zephyr] Python requirements
+  - platform's [Zephyr][zephyr] toolchain
+
+#### dev
+
+For _developing_ [ZMK][zmk] (firmware and documentation).
+
+- FROM: **build**
+- Includes:
+  - remaining [Zephyr][zephyr] dependencies (`apt-get`)
+  - build and test [Zephyr][zephyr] Python requirements
+  - other useful development packages
+
+[debian]: https://hub.docker.com/_/debian "Debian"
+[zephyr]: https://github.com/zephyrproject-rtos/zephyr "Zephyr"
+[zmk]: https://github.com/zmkfirmware/zmk "ZMK"