How to make white label React app

Issue #654

Use shelljs to execute shell commands, and fs to read and write. In public/index.html specify some placeholder and we will replace those in our script

const fs = require('fs');
const shell = require('shelljs')

let indexHtml = fs.readFileSync(publicIndexHtmlPath, 'utf8')
indexHtml = indexHtml
    .replace('CONSTANT_HTML_TITLE', `${app.name} - ${app.headline.title}`)
    .replace('CONSTANT_HTML_META_DESCRIPTION', app.headline.text)

fs.writeFileSync(publicIndexHtmlPath, indexHtml)

// build
shell.cd('projects/my_react_app')
shell.exec('npm run build')

// copy
shell.exec(`cp -a projects/my_react_app web_server/public`)