Readded io_expander.c #509

	name: Platform IO CI
	on: [push]
	jobs:
	build:
	name: Build
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v4
	with:
	submodules: recursive
	- uses: actions/cache@v4
	with:
	path: \|
	~/.cache/pip
	~/.platformio/.cache
	key: ${{ runner.os }}-pio
	- name: Set up Python
	uses: actions/setup-python@v5
	with:
	python-version: "3.10"
	- name: Install PlatformIO
	run: python -m pip install -U platformio
	- name: Build firmware
	run: pio run

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