docs: update gatsby develop overview for query on demand

Author: pieh

docs/docs/conceptual/overview-of-the-gatsby-build-process.md

@@ -56,7 +56,7 @@ success onPostBootstrap - 0.130 s
 info bootstrap finished - 3.674 s
 ⠀
 success run static queries - 0.057 s — 3/3 89.08 queries/second
-success run page queries - 0.033 s — 5/5 347.81 queries/second
+success run page queries - 0.026s - 3/3 114.85/s
 success start webpack server - 1.707 s — 1/1 6.06 pages/second
 ```
 
@@ -136,8 +136,9 @@ success onPostBootstrap - 0.130 s
 info bootstrap finished - 3.674 s
 ⠀
 success run static queries - 0.057 s — 3/3 89.08 queries/second
-success run page queries - 0.033 s — 5/5 347.81 queries/second
+- success run page queries - 0.033 s — 5/5 347.81 queries/second
 - success start webpack server - 1.707 s — 1/1 6.06 pages/second
++ success run page queries - 0.026s - 3/3 114.85/s
 + success Generating image thumbnails — 6/6 - 1.059 s
 + success Building production JavaScript and CSS bundles - 8.050 s
 + success Rewriting compilation hashes - 0.021 s
@@ -151,6 +152,8 @@ There is only one difference in the bootstrap phase where HTML and CSS is delete
 
 By omitting these later steps, `gatsby develop` can speed up your ability to make live edits without page reloads using features like [hot module replacement](/docs/glossary#hot-module-replacement). It also saves time with the more CPU intensive processes that aren't necessary to perform in rapid development.
 
+There is also difference in amount of page queries that will run. `gatsby develop` will run at most 3 page queries (index page, actual 404 and develop 404) initially. Rest of the queries will run when they will be needed (when browser requests them). In contrast, `gatsby build` will run page queries for every page that doesn't have cached and up to date results already.
+
 A [cache](/docs/glossary#cache) is also used to detect changes to `gatsby-*.js` files (like `gatsby-node.js`, or `gatsby-config.js`) or dependencies. It can be cleared manually with the `gatsby clean` command to work through issues caused by outdated references and a stale cache.
 
 ## What happens when you run `gatsby build`?