Motivation:
NIOTS will not work on Linux but we can at least make it not fail
compilation when compiled on Linux. That way consumers of the API can
depend on NIOTS but make sure they only use NIOTS when wrapped in a
`#if canImport(Network)` block.
Modification:
Guard everything by `#if canImport(Network)`
Result:
This package will now build on Linux (without providing any useful
code).