process.stdin stream for passing into new process.spawn equivalent (process.create?)

[Corecii]

Created from a Discord conversation

[1:49 PM] (Erica) DevComp: ill implement a process.stdin which hands you the stdin you were given
[1:49 PM] (Erica) DevComp: and you can put that in SpawnOptions
[1:50 PM] Shae (Corecii): that would work great, thank you for your work on this!
[6:31 AM] (Erica) DevComp: can you create an issue on lune for this
[6:31 AM] (Erica) DevComp: i want to get this done in this week and I might forget

This would allow for a simple way to pass the Lune process's stdin into a process created with the process API, allowing user input.

[CompeyDev]

As #211 introduces reader and writer streams into lune, this can be leveraged to have a process.stdin reader stream quite trivially, following it being merged.