Feat: Add Loop property

[CodeYan01]

Makes it easier to toggle looping, and prevents flickering that would be caused by calling TkinterVideo.play() after the "<>" event.

Fixes #32

[CodeYan01]

I only made it a property (with get/setter) for consistency with other functions like keep_aspect and set_resampling_method having setter functions that don't really do anything else. But having a getter too imo is important if you're gonna have a setter, so I made it a Python property for completeness

[PaulleDemon]

Hi, I am currently will look into this as soon as I am free

[Brandon4466]

This is a REQUIRED change. Not because of the reason though. This is required because the original documented way to loop causes a massive memory leak. Just replaying in that way creates a new instance in memory and does not release the old instance from memory and Python's GC does not catch and drop it. After 3-4 mins a 3 second video fills up 2GB+ of RAM. This change here fixes the memory leak because it uses the same instance. This isn't the perfect implementation, but may be the best possible. Implementing in this way causes the video to be unable to be changed unless you destroy the widget entirely and have it reestablished which is inconvenient. This is because it will continue loop forever, not looking for changes without ever breaking (Line 194+195). This does NOT stop the flickering and jittering. I don't know if there is a better solution to implement this given how tkinter is constructed. If you wrap the load and play lines in a function and thread that using threading that DOES get rid of the flickering, however it does not get rid of the stuttering every ~1sec.

[PaulleDemon]

Ok, I am looking into this. @Brandon4466 can you help me understand which part is not being Garbage collected? I will try to implement this ASAP

[CodeYan01]

@Brandon4466 were you suggesting changes to this PR? Because on github it shows that you are suggesting changes but I don't see anything new that you changed.

[havetc]

Just two very minor suggestions, to have more consistency in the code base