Add SpirvHelper (Shader cross compilation)

- Make OpenGL2 and OpenGL3 use the same base shaders (using SpirvHelper)
- Add Transpose func to Mat4

backends/include/pd_system/spirv-helper.hpp

@@ -0,0 +1,36 @@
+#pragma once
+
+#include <glslang/Public/ResourceLimits.h>
+#include <glslang/Public/ShaderLang.h>
+
+#include <pd/common.hpp>
+
+namespace PD {
+class SpirvHelper {
+ public:
+  enum class Format {
+    GLSL,
+    HLSL,
+    MSL,  // Not supported yet
+    SPIRV,
+  };
+
+  enum class Stage {
+    Vertex = 0,
+    Geometry = 3,
+    Fragment = 4,
+  };
+
+  SpirvHelper() = default;
+  ~SpirvHelper() = default;
+
+  static void Init();
+  static void Finalize();
+  static void SetupResources(TBuiltInResource& resources);
+  static std::vector<PD::u32> GLSL2SPV(Stage stage, const char* code,
+                                       bool vulkan_mode = false);
+  static std::string SPV2GLSL(const std::vector<PD::u32>& spirv, int version,
+                              bool es = false);
+  static std::string SPV2HLSL(const std::vector<PD::u32>& spirv, int version);
+};
+}  // namespace PD