[docs][guides] update Building With Components page with non-page components #15195
Description
Summary
In reviewing #15079, I wanted to link to the Building with Components Conceptual Guide but noticed it doesn't cover everything it should. There are sections on Page Components and Page Template Components, and then it goes into html.jsx, and doesn't mention anything else.
It would really help users of StaticQuery and PageQuery to know what "non-page components" means in detail, and this page would be a great place to expand on that. Ideally, we could craft a new bit of text that rephrases the definition in a new way rather than copying so if the other explanations don't make sense to someone, they'll get another chance to understand. This is a Conceptual Guide, so deeper technical explanations are welcome.
The html.jsx section should probably also explicitly mention that overriding html.js is optional. It mentions it in the third paragraph with "Typically you should omit this from your site", but it should be more clearly stated in the first sentence or two that you don't need to create that file unless you've got a specific reason.
The page to update: https://www.gatsbyjs.org/docs/building-with-components/
With these related pages and an updated Conceptual Guide, we'll have more explanations throughout the docs for extra clarity on component types: