Navigation menu & themes

[dons20]

Hey @duckness, great work on the site, I just had a few suggestions (which perhaps I could do a PR for if you agree to them).

• Allow a light/dark mode toggle
  • The current background probably won't be everyone's favourite, and I personally don't like the particular tint is has. Nonetheless if it had a light mode it would be a lot more neutral and appealing.
• Have an easily accessible navigation to each item in a category.
  • By default, the Mask of Goblin sends everyone to Kasel's particular page, which only has a search to the top right and no other obvious navigation.
  • Same applies to the Artifacts. (Perhaps they could be populated on the same page since they aren't as detailed?)
• Possibly split hero pages into Attributes and Skill Details via an easily accessible tab to reduce scrolling.
  • This one isn't as necessary since there is a pretty useful navigation to the top left of the hero section.
• Highlight values that change when stats are modified
  • It would be easier to see values that are modified when leveling up or increasing transcendence levels by putting them bold, giving them a unique color and/or adding a background color.

Those are my main ideas to help improve this project. I'm willing to make PRs for most/all of these as long as you want them to be added.

Thanks