VideoBackends / VideoCommon: add support for specifying include files in shader code

Source/Core/VideoBackends/D3DCommon/Shader.h

@@ -20,7 +20,8 @@ public:
   BinaryData GetBinary() const override;
 
   static std::optional<BinaryData> CompileShader(D3D_FEATURE_LEVEL feature_level, ShaderStage stage,
-                                                 std::string_view source);
+                                                 std::string_view source,
+                                                 VideoCommon::ShaderIncluder* shader_includer);
 
   static BinaryData CreateByteCode(const void* data, size_t length);