check float texture extension, use float32 or float16 if available, show extension on title bar, add thread and render task for lightmap rendering

src/shader.h

@@ -110,6 +110,8 @@ class ShaderManager
     static Shader* m_current;
 public:
     static bool ext_framebuffer_fetch;
+    static bool ext_texture_float;
+    static bool ext_half_float_pixel;
     static bool load(kShader id, const std::string& path);
     static bool reload();
     static bool create(kShader id, const std::string& vertex, const std::string& fragment);