[examples] use le_exr in lut_grading example

add a dependency on le_exr to lut_grading example, so that we may test
le_exr using CI

this also demonstrates how to add a decoder for a new file type to
le_resource_manager.

apps/examples/lut_grading_example/lut_grading_example_app/CMakeLists.txt

@@ -9,9 +9,8 @@ depends_on_island_module(le_ui_event)
 depends_on_island_module(le_renderer)
 depends_on_island_module(le_pipeline_builder)
 depends_on_island_module(le_camera)
-
-depends_on_island_module(le_pixels)
 depends_on_island_module(le_resource_manager)
+depends_on_island_module(le_exr)
 
 set (SOURCES "lut_grading_example_app.cpp")
 set (SOURCES ${SOURCES} "lut_grading_example_app.h")

apps/examples/lut_grading_example/lut_grading_example_app/lut_grading_example_app.cpp

@@ -5,6 +5,7 @@
 #include "le_pipeline_builder.h"
 #include "le_resource_manager.h"
 #include "le_ui_event.h"
+#include "le_exr.h" // provides the exr image decoder interface
 
 #include <iostream>
 #include <memory>
@@ -51,6 +52,10 @@ static lut_grading_example_app_o* lut_grading_example_app_create() {
 
 	app->renderer.setup( le::RendererInfoBuilder( app->window ).build() );
 
+	// This is how you introduce a new image decoder to resource_manager -
+	// Now you could open '.exr' images using the resource_manager...
+	app->resource_manager.set_decoder_interface_for_filetype( "exr", le_exr_api_i->le_exr_image_decoder_i );
+
 	char const* hald_lut =
 	    "./local_resources/images/night_from_day.png";
 	//	    "./local_resources/images/hald_8_identity.png";  // pass-through