Add looping and muted properties to the sound object

[literary-programmer]

The sound object has a play_looped() method that allows a sound to keep repeating. However, there is currently no way to check if a sound is looping. Please add a bool looped property to the sound object, so users can set and get this property.

Muting is an important feature for sounds. Unfortunately, neither BGT nor NVGT provides built-in support for muting. Developers currently have to manually set the sound volume to -100 to mute and back to 0 to unmute. I propose adding true muting functionality to the sound object. When a sound is muted, it should store the current volume. Upon setting the muted property to false, the volume should be restored to its previous value.

Please consider adding these features as they would offer greater control over sound management.

Thank you.