[docs] add doc on "Life and Times of a Gatsby Build"

[marcysutton]

Summary

Through feedback provided on gatsbyjs.org, it has become clear that the stub article on Life and Times of a Gatsby Build is an important one that needs filling out to explain Gatsby concepts: https://www.gatsbyjs.org/docs/life-and-times-of-a-gatsby-build/

"This is possibly the most important page and it's empty!"

This page is a stub in the Conceptual Guide section, and would be a great opportunity to clarify what happens at build time vs. runtime. I couldn't find a GitHub issue for it, so I created this one to capture it as something we need.

There was a related question about the doc on Client Data Fetching, which assumes a lot of knowledge about build time vs. runtime processes. A dedicated doc on this would be very helpful, and this seems like a good one.

[m-allanson]

I made a start on this, but didn't get to the main "what's actually happening" section. Posting here in case someone else gets to this before me.

---

Life and Times of a Gatsby Build

Building with Gatsby

Gatsby is a framework for creating web sites and web apps. As part of creating your site you’ll provide Gatsby with the code, configuration and data it needs to output a speedy, optimised site.

When working with Gatsby it has two modes. You can start gatsby in either mode by running gatsby develop or gatsby build.

gatsby develop

Gatsby develop is optimised for rapid feedback and extra debugging information.

Using gatsby develop runs a server in the background enabling useful features like hot reloading and Gatsby’s data explorer.

gatsby build

You’ve added the finishing touches to your site and everything looks great. What now? This is where the build step comes in. Run gatsby build to create a version of your site with

will package up your site’s config, data, and code then optimise the heck out of it, and finally

What happens when you run gatsby build

This is a high-level overview. For more detailed information, check TODO, TODO, TODO.

[alexluong]

I happened to write a blog post covering this topic. It's a bit more anecdotal as I describes what's going on with codes, but I think some part of it can be recycled to a documentation page.

If you're interested, you can find it here.

Would love to hear your thoughts on it and hope that it helps writing this doc!