Add VRChat and GitHub packages to Unity project

Assets/VRCSDK/Dependencies/VRChat/Scripts/MaterialFallback/FallbackMaterialCache.cs

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+using System;
+using System.Collections.Generic;
+using System.Linq;
+using UnityEngine;
+using VRC.Core;
+
+public class FallbackMaterialCache
+{
+    private readonly Dictionary<Material, Material> _fallbackMaterialCache = new Dictionary<Material, Material>();
+
+    public void AddFallbackMaterial(Material material, Material fallbackMaterial)
+    {
+        if(!_fallbackMaterialCache.ContainsKey(material))
+        {
+            _fallbackMaterialCache.Add(material, fallbackMaterial);
+        }
+        else
+        {
+            Debug.LogError(string.Format("Attempted to add a duplicate fallback material '{0}' for original material '{1}'.", fallbackMaterial.name, material.name));
+        }
+    }
+
+    public bool HasFallbackMaterial(Material material)
+    {
+        return _fallbackMaterialCache.ContainsKey(material);
+    }
+
+    public Material GetFallBackMaterial(Material material)
+    {
+        return _fallbackMaterialCache[material];
+    }
+
+    public void Clear()
+    {
+        Material[] cachedFallbackMaterials = _fallbackMaterialCache.Values.ToArray();
+        for(int i = cachedFallbackMaterials.Length - 1; i >= 0; i--)
+        {
+            UnityEngine.Object.Destroy(cachedFallbackMaterials[i]);
+        }
+
+        _fallbackMaterialCache.Clear();
+    }
+}