Re-add NVDEC project (not integrated)

Ryujinx.Graphics.Nvdec/VDec/FFmpegFrame.cs

@@ -0,0 +1,14 @@
+namespace Ryujinx.Graphics.VDec
+{
+    unsafe struct FFmpegFrame
+    {
+        public int Width;
+        public int Height;
+
+        public byte* LumaPtr;
+        public byte* ChromaBPtr;
+        public byte* ChromaRPtr;
+
+        public byte[] Data;
+    }
+}