refactor GLSLExtension.cpp & add 'param' shader preprocessor directive & add PostEffect class (WIP)

src/graphics/core/PostEffect.cpp

@@ -0,0 +1,15 @@
+#include "PostEffect.hpp"
+
+#include "Shader.hpp"
+
+PostEffect::Param::Param() : type(Type::FLOAT) {}
+
+PostEffect::Param::Param(Type type) : type(type) {}
+
+PostEffect::PostEffect(std::unique_ptr<Shader> shader)
+    : shader(std::move(shader)) {
+}
+
+void PostEffect::use() {
+    shader->use();
+}