docs: update README, add CONTRIBUTING #10

	---
	name: Docker Image
	# Multi-platform Docker image build
	#
	# Reference:
	# - https://docs.docker.com/build/ci/github-actions/multi-platform/
	# - https://docs.docker.com/build/ci/github-actions/cache/

	on:
	push:
	branches:
	- main
	tags:
	- v*

	env:
	REGISTRY: ghcr.io
	IMAGE_NAME: ccache-exporter

	jobs:
	docker-image:
	runs-on: ubuntu-latest
	permissions:
	contents: read
	packages: write
	steps:
	- name: Checkout
	uses: actions/checkout@v4

	- name: Log in to the Github Container Registry
	uses: docker/login-action@v3
	with:
	registry: ${{ env.REGISTRY }}
	username: ${{ github.repository_owner }}
	password: ${{ secrets.GITHUB_TOKEN }}

	- name: Set up QEMU
	uses: docker/setup-qemu-action@v3

	- name: Set up Docker Buildx
	uses: docker/setup-buildx-action@v3

	- name: Cache Docker layers
	uses: actions/cache@v4
	with:
	path: /tmp/.buildx-cache
	key: ${{ runner.os }}-buildx-${{ github.sha }}
	restore-keys: \|
	${{ runner.os }}-buildx-

	- name: Extract Docker metadata
	id: meta
	uses: docker/metadata-action@v5
	with:
	images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
	tags: \|
	type=raw,value=latest,enable={{is_default_branch}}
	type=ref,event=branch
	type=ref,event=pr
	type=semver,pattern={{version}}
	type=semver,pattern={{major}}.{{minor}}

	- name: Build and push
	uses: docker/build-push-action@v6
	with:
	cache-from: type=local,src=/tmp/.buildx-cache
	cache-to: type=local,dest=/tmp/.buildx-cache
	platforms: linux/amd64,linux/arm64
	push: true
	tags: ${{ steps.meta.outputs.tags }}
	labels: ${{ steps.meta.outputs.labels }}

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