fix: Enhance contact shadows

[FarazzShaikh]

Why

What

Fixes the following issues in ContactShadows

• Handles case where autoClear: false is set on <Canvas />
• Respects castShadow property on meshes
  • Useful for excluding meshes from Contact Shadows, this is not possible in the current implimentation.
  • This also makes the shadows less expensive
• Respects customDepthMaterial to allow for shaders to affect the shadow. See attached box and video.
  • Notice the contact shadow mirroring into alpha falloff and displacement of the mesh. This is because a customDepthMaterial is provided.
  • Using customDepthMaterial means that the distance attentuation feature will be left up to the user to impliment within their customDepthMaterial.
• Refactors some of the code to improve readibility
• Clean up resources allocated in useMemo

Box: https://codesandbox.io/s/black-leftpad-jmfyjm

React.App.-.Google.Chrome.2023-07-23.00-40-47.mp4

Vite.+.React.+.TS.-.Google.Chrome.2023-07-22.21-10-16.mp4

Checklist

• Documentation updated (example)
• Storybook entry added (example)
• Ready to be merged

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Name	Status	Preview	Comments	Updated (UTC)
drei	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Jul 22, 2023 7:13pm

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[drcmda]

but wouldn't it be very expensive, given a large scene, to do this every frame?