Introducing an async library inspired by Go in Nim

[Araq]

    ## Maybe in another thread now ?
        echo myString #-> this is unsafe!
        echo repr(myRef) #-> this is unsafe!
    
    
    
    Run

This is now safe, the heap is shared in 2.0. There is also a switch 
`mm:atomicArc` that makes the refcounting itself threadsafe (which your example 
does not need).