Add watcher to react to pageSize changes

[SoloSynth1]

FIrst of all, thank you for making this amazing component!

In my current project, I need to implement variable pageSize for users to choose, but couldn't find an elegant way to do it. So I ended up forking the source code and add a watcher to watch for pageSize changes.

It would be great if the library can support this natively. Thank you!