docs: Specify test running prerequisites in CONTRIBUTING.md #314

	# Copyright 2023 Google LLC
	#
	# Licensed under the Apache License, Version 2.0 (the "License");
	# you may not use this file except in compliance with the License.
	# You may obtain a copy of the License at
	#
	# http://www.apache.org/licenses/LICENSE-2.0
	#
	# Unless required by applicable law or agreed to in writing, software
	# distributed under the License is distributed on an "AS IS" BASIS,
	# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	# See the License for the specific language governing permissions and
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	name: Lint
	on: [pull_request]

	jobs:
	lint:
	runs-on: ubuntu-latest
	permissions:
	contents: read
	concurrency:
	group: ${{ github.workflow }}
	cancel-in-progress: true

	steps:
	- name: Checkout Repository
	uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4

	- name: Install ShellCheck
	run: sudo apt install shellcheck

	- name: Lint Shell Scripts
	run: \|
	set +e
	shellcheck tools/*.sh # See all warnings
	shellcheck --severity error -f quiet tools/*.sh # Fail on errors only

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