(inquiry) add info about valueAt() in sndbuf.ck example

[mariobuoninfante]

Hi,

I was wondering if we could add some info about how .samples() and .valueAt() work in the sndbuf.ck example. More info can be found here: https://lists.cs.princeton.edu/pipermail/chuck-users/2021-June/008961.html

Cheers, Mario