Update example project to 2021 edition #101

	name: Deploy

	on:
	push:
	branches:
	- master
	paths:
	- book/**
	- .github/workflows/site.yml
	workflow_dispatch:

	jobs:
	deploy:
	name: Deploy
	runs-on: ubuntu-latest
	permissions:
	contents: write
	timeout-minutes: 30
	steps:
	- uses: actions/checkout@v3
	- uses: dtolnay/install@mdbook
	- run: mdbook --version

	- name: Build
	run: book/build.sh

	- name: Push to gh-pages
	working-directory: book/build
	run: \|
	REV=$(git rev-parse --short HEAD)
	git init
	git remote add upstream https://x-access-token:${{secrets.GITHUB_TOKEN}}@github.com/dtolnay/cxx
	git config user.name "CXX"
	git config user.email "dtolnay+cxx@gmail.com"
	git add -A .
	git commit -qm "Website @ ${{github.repository}}@${REV}"
	git push -q upstream HEAD:refs/heads/gh-pages --force

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