Add the ability to swap between 2D and 3D gallery objects.

[Rakadeja]

• Add a Button into 'routes/gallery/page.svelte,' for toggling between the display of 2D and 3D gallery objects.

• 3D gallery object's CSS. (Likely going to use .frame-3d)
  Not really necessary to make it that different. We'll see how it scales inside of the 'gallery > art-piece' style.

• Put 3D related styles into their own SCSS/CSS.
  Currently, 3D related CSS is all lobbed into styles.css.

• Add support for 3D gallery objects.
  Modify the gallery to be able to properly load in 3D models from a .json.
  Will have to try loading them in the actual order they're displayed. Not sure how it's going to try loading them - TBD.

• Using ThrelteScene.svelte with simple, non-animated gltf models to begin with.
  Simple rendering test, instead of struggling with animations again.