Add option to disable touch on the invisible track

[tom5079]

It would be nice to have some kind of option to disable touch on the invisible track
Sometimes users touch it accidentally without knowing that it would actually move to that position.

[shahsurajk]

@tom5079 Let's add reference this issue in #32 by amending the last commit message

[tibbi]

just comment out trackView.setOnTouchListener(touchListener) at

RecyclerView-FastScroller/recyclerviewfastscroller/src/main/java/com/qtalk/recyclerviewfastscroller/RecyclerViewFastScroller.kt

Line 498 in 0ba9c9a

trackView.setOnTouchListener(touchListener)

for it. Do not be confused by it not working in the sample app, the recyclerView actually has side margins and it doesn't go below the track. Pretty bad UX I'd say :)