add audio_manager and code refactoring

docs/museums/radio/museum_radio.gd

@@ -2,6 +2,7 @@ extends Node3D
 
 @onready var radio: Radio = $%Radio
 @onready var button_pause_resume: Button = $%Button_Pause_Resume
+@onready var settings_menu: SettingsMenu = $%SettingsMenu
 
 func _on_button_play_pressed() -> void:
 	if !radio.playing:
@@ -28,3 +29,7 @@ func _on_button_next_pressed() -> void:
 
 func _on_button_previous_pressed() -> void:
 	radio.prev_track()
+
+
+func _on_button_settings_menu_pressed() -> void:
+	settings_menu.visible = !settings_menu.visible