POCs written in Rust

Here are the POCs in the chronological order:

• structured_concurrency is adapted from the code of the Rust Book final project, but has a few differences. Notably, it uses the structured concurrency paradigm.

• bin_from_ninja combines Make and Ninja to compile and check the Rust programs backup, synchronize_backup and synchronize_partially, and deploy the binaries to $HOME/bin, thanks to the build.ninja file written by ninja_bootstrap.
  It also uses Pixi, but this dependency is optional.

• coroutine shows a coroutine example and compares it to generic programming for decoupling algorithm from I/O.