Update 2021.4.md #800

	name: Build Documentation

	on:
	push:
	branches:
	- master

	jobs:
	build:

	runs-on: ubuntu-latest

	steps:

	# Setup .NET SDK
	- name: Dotnet Setup
	uses: actions/setup-dotnet@v3
	with:
	dotnet-version: 6.x

	# Checkout repo
	- name: Checkout repo
	uses: actions/checkout@v1
	with:
	fetch-depth: 1

	# Install DocFX 2.71.0
	- name: Install DocFX
	run: dotnet tool update -g docfx --version 2.71.0

	- name: Build documentation
	run: ./build.bat

	- name: SFTP Deploy
	uses: wlixcc/SFTP-Deploy-Action@v1.0
	with:
	username: root
	server: 78.47.109.137
	#port: # default is 22
	# you can copy private_key from your *.pem file, keep format
	ssh_private_key: ${{ secrets.SSH_PRIVATE_KEY }}
	# will put all file under this path
	local_path: ./_site/* # default is ./*
	# files will copy to under remote_path
	remote_path: /var/www-thegraybook # default is /
	# sftp args
	# args: # optional

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