Clean up look and structure

[hyrodium]

Copied from: https://github.com/JuliaPackageComparisons/JuliaPackageComparisons.github.io/pull/47#issuecomment-1891008330

• [ ] Add meta-section in the sidebar (https://github.com/JuliaPackageComparisons/JuliaPackageComparisons.github.io/issues/22)
• [x] Search (https://github.com/JuliaPackageComparisons/JuliaPackageComparisons.github.io/issues/3)
• [ ] Add logo (https://github.com/JuliaPackageComparisons/JuliaPackageComparisons.github.io/issues/51)
• [x] #70
• [ ] Add "copy to clipboard" button to each code block
• [ ] Add darkmode

[KronosTheLate]

• [ ] Make it so that the sidebar does not scroll to the top each time a section is clicked

[KronosTheLate]

The current headings look a little too similar to me, and without numbering it can be hard to see the section depth. It would be nice to distinguish their style more, by changing the font-size, color, adding an underline etc.