Is the real problem about discoverability in the documentation? [Difference of two sets](https://nim-lang.org/docs/system.html#-,set%5BT%5D,set%5BT%5D) is already there, though not with `seq`.
Do we need to improve the documentation search engine ([CTRL]+[F])? Do we need better or more descriptive proc names? Should we search also in the description of the procs or by categories?
