Add a dark theme

[Fleker]

I've enjoyed playing this game for a while, but it can definitely be a tad hard on the eyes. Adding a dark theme as an option can provide a nice UX and be consistent with other software and apps I use, including GitHub.

I can tackle this PR.

[nk9]

That would be great! I use dark mode and would love to see it for this game as well.

[hryanjones]

@lanodan I don't suppose it's easy for you to add a toggle for folks who want to toggle it a specific way? I've had a user complain that they like some of their sites dark, but didn't want it for Guess My Word.

[lanodan]

Should be doable, opened #70 to be able to select it.

[Bratface23]

@lanodan I don't suppose it's easy for you to add a toggle for folks who want to toggle it a specific way? I've had a user complain that they like some of their sites dark, but didn't want it for Guess My Word.

Thanks, hryanjones! That was me, Bratface23!

[hryanjones]

Thanks for the start @lanodan ! I added onto your commit to make it save to and load from localstorage.

[hryanjones]

I had to revert these changes as it was breaking the leaderboard page. Can revisit this with better support on all pages.