added a slight transition effect when toggling theme

[GAsplund]

While I like the idea, I'm not sure how it should be implemented. On one hand, it does look cool when the entire site transitions between light and dark theme, but on the other, transitioning might feel a bit sluggish with the way it does it right now.

I would like to approve this, but I would suggest some changes:

• Use a transition for specific properties - placing a transition on everything can have unintended side effects (look at the search bar), I suggest using transition: background-color 0.3s ease, color 0.3s ease, border-color 0.3s ease; which remediates the symptom but does not remove it entirely.
• Maybe speed it up a bit? I've experimented and found that 0.15s or 0.2s feel better (for me personally)

[simon-wg]

Good point! I'll take a look and see what I can do to make it feel snappier.