Update docs on Build Modes to share information about size of the build output for deployment/performance

[drewgallagher]

Looking at the build mode docs I don't see anything that says that a production build should be slimmer and faster to deploy/run than a non-prod build.

I am inferring this based on the slower non-prod deployment times for the same build command with varying env for our react app.

To help other devs and to make it clear in the docs can we add the difference between a production and non prod build here? https://vite.dev/guide/env-and-mode

I think this will be helpful to beginners or those new to vite that haven't seen this before with other node build tools