feat: add assets access to gui elements

sonic-radiance.love/birb/modules/gui/elements/parent.lua

@@ -13,6 +13,7 @@ function GuiElement:new(name, x, y, w, h)
     self.depth = 0
 
     self.tweens = TweenManager(self)
+    self.assets = self:getAssets()
 
     self:register()
 end
@@ -22,6 +23,11 @@ function GuiElement:getGui()
     return scene.gui
 end
 
+function GuiElement:getAssets()
+    local scene = core.scenemanager.nextScene or core.scenemanager.currentScene
+    return scene.assets
+end
+
 function GuiElement:register()
     local gui = self:getGui()
     self.creationId = gui:addElement(self.name, self)