[Feature Request] - Partial Library Re-Scan

[yuval-ziv]

After adding new songs to my library, I need to refresh my library for new changes.
Is there a way to run a partial run, only looking for files that don't exist, or even their modified time to reduce refresh time?

[wilywyrm]

I took a whack at implementing this in #280 @tranxuanthang if you could take a look when you have a spare moment.