Rewrite Contentful sample in rxjs and async/await

sample-by-async-index.js

const contentful = require('contentful')
const chalk = require('chalk')
const Table = require('cli-table2')
const argv = require('yargs').argv

const Rx = require('rxjs/Rx')
const Observable = require('rxjs/Observable').Observable

const spaceId = argv.spaceId
const accessToken = argv.accessToken

const client = contentful.createClient({
    space: spaceId,
    accessToken: accessToken
})

Observable
    .defer(async () => {
        const contentTypes = await client.getContentTypes()

        const firstItem = contentTypes.items[0]

        const response = await client.getEntries({
            content_type: firstItem.sys.id
        })

        return { displayField: contentTypes.items[0].displayField, entries: response.items }
    })
    .subscribe(({displayField, entries}) => {
        const table = new Table({
            head: ['Id', 'Title']
        })
        entries.forEach((entry) => {
            table.push([entry.sys.id, entry.fields[displayField] || '[empty]'])
        })
        console.log(table.toString())
    })