specify whether flixel projects need to pass html5/c++ compilation

projects/nat-flixel-desktop-playground/source/import.hx

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+import flixel.FlxGame;
+import openfl.display.Sprite;
+import flixel.FlxState;
+import flixel.ui.FlxButton;
+import flixel.FlxG;
+import flixel.FlxSprite;
+import flixel.util.FlxColor;
+import flixel.input.keyboard.FlxKey;
+import flixel.math.FlxPoint;
+import flixel.math.FlxVelocity;
+import flixel.FlxObject;
+import flixel.tile.FlxTilemap;
+import flixel.group.FlxGroup;
+import flixel.tweens.FlxTween;
+import flixel.tweens.FlxEase;
+import kiss.Prelude;