Update alpine Docker tag to v3.21.0 #89

	name: Dockerlint
	on:
	push:
	pull_request:
	workflow_dispatch:
	jobs:
	docker-lint:
	runs-on: ubuntu-latest
	name: docker-lint
	steps:
	- name: Checkout
	uses: actions/checkout@v4
	- name: Install hadolint
	run: \|
	sudo wget https://github.com/hadolint/hadolint/releases/latest/download/hadolint-Linux-x86_64 -O /usr/bin/hadolint
	sudo chmod +x /usr/bin/hadolint
	- name: run lint
	run: \|
	DOCKERFILES="$(find . -name "Dockerfile")"
	for file in $(echo "$DOCKERFILES" \| tr " " "\n"); do
	# DL3003 warning: Use WORKDIR to switch to a directory
	# DL3007 warning: Using latest is prone to errors if the image will ever update. Pin the version explicitly to a release tag
	# DL3018 warning: Pin versions in apk add. Instead of `apk add <package>` use `apk add <package>=<version>`
	# DL3013 warning: Pin versions in pip. Instead of `pip install <package>` use `pip install <package>==<version>` or `pip install --requirement <requirements file>`
	hadolint "$file" --ignore DL3003 --ignore DL3007 --ignore DL3013 --ignore DL3018 \| tee -a hadolint.log
	done
	if grep -q "DL[0-9]\+\\|SC[0-9]\+" hadolint.log; then
	exit 1
	fi

Provide feedback