Content migration - add "Deploying to Now" doc

[amberleyromo]

Issue Context

This issue is part of the content migration project (#8103), which is meant to take existing content and repurpose it so it's easier to find in the docs.

Motivation

We are doing this because many people have written excellent content that we want to canonize and maintain so more people can find it and benefit from it.

Steps to resolve this issue

1. Read the Style Guide and follow it in order for your PR to be accepted. Pay special attention to the templates.

• Style Guide: https://www.gatsbyjs.org/docs/gatsby-style-guide/
• Docs Templates: https://www.gatsbyjs.org/docs/templates/
• Example of a guide to imitate: https://www.gatsbyjs.org/docs/deploying-to-s3-cloudfront

2. Create the "Deploying to Now" article by creating a file named deploying-to-now.md in this directory.

3. Copy and paste this section of the deploying doc: https://www.gatsbyjs.org/docs/deploy-gatsby/#now

4. Make sure you adjust the content to follow the format listed in these resources:

• Docs Templates: https://www.gatsbyjs.org/docs/templates/
• Example of a guide to imitate: https://www.gatsbyjs.org/docs/deploying-to-s3-cloudfront

5. Link the new doc in the docs sidebar file, doc-links.yml, under the Deploying section:

- title: Deploying to Now
  link: /docs/deploying-to-now

[amberleyromo]

Open PR: #8729