Add `Array#at` polyfill #1230

	name: CI
	on: [push]
	jobs:
	build:
	runs-on: ubuntu-latest

	steps:
	- uses: actions/checkout@v2

	- name: Use yarn global cache
	uses: actions/setup-node@v3
	with:
	node-version: 16
	cache: 'yarn'

	- name: Install dependencies
	run: yarn install --frozen-lockfile
	env:
	CI: true

	- name: format
	run: yarn format
	env:
	CI: true

	- name: lint
	run: yarn lint
	env:
	CI: true

	- name: Test
	run: yarn test --ci --coverage --maxWorkers=2
	env:
	CI: true

	- name: Build
	run: yarn build
	env:
	CI: true

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