add howto on image builds #45

	name: Build PRs

	on:
	pull_request:

	jobs:
	docker:
	runs-on: ubuntu-latest
	services:
	registry:
	image: registry:2
	ports:
	- 5000:5000
	steps:
	- name: Checkout
	uses: actions/checkout@v2
	- name: Set up QEMU
	uses: docker/setup-qemu-action@v1
	- name: Set up Docker Buildx
	uses: docker/setup-buildx-action@v1
	with:
	driver-opts: network=host
	- name: Build
	uses: docker/build-push-action@v2
	with:
	context: .
	platforms: linux/amd64
	push: true
	tags: localhost:5000/opendronemap/nodeodm:test
	- name: Test Powercycle
	run: \|
	docker run --rm localhost:5000/opendronemap/nodeodm:test --powercycle

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