Overflowing table of contents is difficult to use on website

If the table of contents overflows beyond the viewport, the user cannot view the rest of the table of contents without scrolling to the bottom of the page. This is particularly inconvenient on long pages like https://cheerio.js.org/docs/api/classes/cheerio/. I have been able to fix this by adding the classes `h-[calc(100vh-var(--spacing)*20)] overflow-y-auto` onto the `div` in the TableOfContents component. I'm willing to make a PR if this works for you.