Only update context when values change to avoid extra re-renders

[cvbuelow]

Currently the context is changing whenever the SwiperSlide is re-rendered since it isn't memoized. This fixes that to reduce re-renders of child components.

[nolimits4web]

Would be good to see the CodeSandbox illustrating both issue and fix

[nolimits4web]

Closing due to inactivity and/or no responses from issue author