docs(contributing): add a guide for checking of `undefined` or `null` #1948

	name: Default CI Pipeline

	on: [push, pull_request]
	jobs:
	setup-and-test:
	runs-on: ${{ matrix.os }}

	strategy:
	matrix:
	os: [ubuntu-latest]
	node-version: [18.x, 20.x]

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

	- name: Use Node.js ${{ matrix.os }} ${{ matrix.node-version }}
	uses: actions/setup-node@v3
	with:
	node-version: ${{ matrix.node-version }}
	cache: "npm"
	- name: Install
	run: npm ci

	- name: Build
	run: npm run build

	- name: Test with coverage report
	run: npm run coverage:only

	- name: Upload to codecov.io
	uses: codecov/codecov-action@v2

	eslint:
	name: eslint
	runs-on: ubuntu-latest
	steps:
	- name: Checkout
	uses: actions/checkout@v2

	- name: Use Node.js 18
	uses: actions/setup-node@v1
	with:
	node-version: 18

	- name: Install
	run: npm ci

	- name: Lint
	run: npm run lint

	version_consistency:
	name: Check version consistency of packages
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v1
	- name: install node v18
	uses: actions/setup-node@v1
	with:
	node-version: 18
	- name: verify packages version consistency accross sub-modules
	run: npm run check:versions

	prettier:
	name: Check coding style
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2
	- uses: actionsx/prettier@v2
	with:
	args: --check .

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