Fix body transition on refresh/dark toggle

[codechriscode]

The body element is rendered before everything else and this breaks dark mode experience when darkMode is set to true in localStorage, because

• If body has a transition time, it transitions smoothly on page load while all else loads with the dark theme already there
• If body does not have a transition time, it flashes when toggling

Possible resolutions:

• Add time transition to body after HTML dark attribute has loaded OR
• Add a container div and not rely on body style

[codechriscode]

Solved on commit 70ea18108559af0ea4abedc4d7f19c0faa400af9