Gatsby SSR colorMode Fix

[fcisio]

This PR follows the issue: #1602

Also extends on my previous PR #1639

I wasn't able to repro the issue inside the package, but basically replicated what I do on the user-side.
It should work, and once there is a canary version, I'll be able to test in my own projects.

Let me know what you guys think 👌

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I additionally fixed some things that were breaking Gatsby builds internally

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[fcisio]

Alright 😅
Diving deeper into this, I realized I don't really have a fix.

I did draft one, but it only works when local storage is turned off.

I'm not sure what causes the issue in the first place, but my guess is it's from preferredMode and modeFromClass.

Steps to reproduce:

1. build docs
2. serve docs
3. delete the theme-ui-color-mode key from the storage
4. navigate to http://localhost:9000/home/

A pink div should show up on dark mode (if it's the preferredMode). The issue is only present on the first load. If you switch to dark mode, then all works fine.

If I remember right, I first saw this issue surface around the time useColorSchemeMediaQuery default was changed to true. We could probably trace back what changes are causing this.

If anyone, wants to have a go at this, I'm kinda stuck for now.

[hasparus]

Closing, because this PR is a leftover. We fixed this already on develop (and fcisio reviewed it)