feat: darkmode

[lmaos-code]

Hi 👋🏾,

I'm an avid user of your BibTeX generator and propose adding a dark mode to enhance the nighttime user experience.

Key Points:

• Introduced dark mode, ensuring consistency with the light theme.
• Implemented a workaround for SSR and dark mode toggle state. I acknowledge that the implemented solution is far from perfect, and I am open for a better solution regarding component hydration.

Note:

• Dark mode isn't available for the admin page due to set up issues on my end with Discord auth.
• Added react-feather for the icons.

Looking forward to your feedback or suggestions to refine this feature.

Thanks for the great tool!

Best,
Manu

[vercel]

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