Readme: update maintenance section (#16) #4

	name: Docker

	on:
	push:
	branches:
	- "master"

	jobs:
	docker:
	runs-on: ubuntu-latest
	strategy:
	matrix:
	include:
	- app: "packagist"
	- app: "solr"

	fail-fast: false

	name: Docker (dockette/packagist:${{ matrix.app }})

	steps:
	- name: Checkout
	uses: actions/checkout@v2

	- name: Login to DockerHub
	uses: docker/login-action@v1
	with:
	username: ${{ secrets.DOCKERHUB_USERNAME }}
	password: ${{ secrets.DOCKERHUB_TOKEN }}

	- name: Set up QEMU
	uses: docker/setup-qemu-action@v1

	- name: Set up Docker Buildx
	uses: docker/setup-buildx-action@v1

	- name: Cache Docker layers
	uses: actions/cache@v2
	with:
	path: /tmp/.buildx-cache
	key: ${{ runner.os }}-buildx-${{ github.sha }}-${{ matrix.app }}
	restore-keys: \|
	${{ runner.os }}-buildx-

	- name: Build and push
	uses: docker/build-push-action@v2
	with:
	context: ${{ matrix.app }}
	push: true
	tags: dockette/packagist:${{ matrix.app }}
	cache-from: type=local,src=/tmp/.buildx-cache
	cache-to: type=local,dest=/tmp/.buildx-cache
	platforms: linux/amd64,linux/arm64

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