Add animations

[Eggrror404]

目前沒多少想法，想到就補 反正社網就亂搞用（

況且這邊沒用 Astro 那感覺 JS 當然是要用好用滿

• [ ] hero section gradient following cursor (slightly moving, likely with a threshold)
• [ ] reveal-on-scroll effect (https://github.com/DaveKeehl/svelte-reveal)
• [ ] gradient somewhere on top (maybe animated from the hero gradient)
• [ ] not an animation, but social links should be added on the nav bar
• [ ] new global menu look, the current one's bad
  • with the menu icon changing to an X, and the popup square extended up, containing the X