Add initial README with project overview

Introduces a README file describing the MoonlightVRC project, its features, performance notes, quick start instructions, editor preview details, tips, and contribution guidelines.

README.md

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+# MoonlightVRC
+
+## Idea
+
+When creating a World for VRChat that reveals items around the player as they walk up to them, I stumbled across the problem that Quest doesn't handle realtime lights well. As a result, you may end up spending tens of hours coding your own light system.
+
+What this includes:
+- Point/spotlights editable at runtime.
+- A couple of premade shaders (standard, particle).
+- Premade code handling lights, normals and a Lambertian diffuse.
+
+Work in progress:
+- Water shader
+- Documentation
+- More performance testing/improvements
+  
+Planned:
+- Basic shadows via a shadow emitter map. The plan is to only sample the highest points of a map area and then calculate if the light ray is intersecting the object. This should provide basic shadow casting that is much more performant than raycasting.
+
+---
+
+## Performance
+
+Early testing showed the Quest 3 dropping to around 30 FPS when having 100 spotlights active in a scene at once. This test was conducted with 5 material targets. Since then the shader has grown in size significantly and I have also included some optimizations in the code transferring light data to the objects. Reading the light data and transferring it to the shader seems to be a major bottleneck at the moment but there is room for improvements.
+
+On PC, I haven't encountered any frame drops in the editor at all, even with 400 concurrent lights.
+
+## Quick start
+
+1. Clone the code into your project.
+
+2. Add the `PlayerPositionsToShader` component to a GameObject in your scene:
+   - Inspect the script in the inspector and assign `targets` (Objects that use a compatible shader) and optional `otherLightSources` (Transforms as described in step 3).
+   - Tweak strength/intensity of the local and remote player if you want them to have an attached light.
+
+3. For lights, attach `LightdataStorage` to a Transform and configure:
+   - `range`, `type`, `color`, `intensity`, and `spotAngleDeg`.
+
+4. Use the provided shader include `Shader/MoonsLight.cginc` in your CGPROGRAM blocks to consume the arrays and compute lighting.
+
+---
+
+## Editor preview
+
+- While not in Play mode, the editor helper `PlayerPositionsToShaderPreview` (EditorPreview/Editor/PlayerPositionsToShaderPreview.cs) writes the same property blocks to assigned Renderers so you can preview emissive/lighting effects in the Scene view. Those update 10 times a second.
+- The editor partial helper for building preview arrays is in `EditorPreview/PlayerPositionsToShader.Editor.cs`.
+
+---
+
+## Tips
+
+- Match `maxLights` in the component with the `#define MAX_LIGHTS` in your shaders (default is 80 — see Performance).
+
+---
+
+## Contributing
+
+If you want to help with development, please contact me on Discord (@demuenu) so we can coordinate our efforts.