feat(library/init/control/coroutine): add `coroutine`

Remark: the termination proofs are commented because Lean 4 is
currently ignoring them and accepting non-terminating functions.

These files are based on an experiment implemented using Lean 3.
We can find it here:
https://gist.github.com/leodemoura/f5d82426c105b5fae0880e77024f6e9c

We will use coroutines to implement the interaction between reader,
elaborator and main driver.
2 files changed