• :dep lines can now be commented out without breaking subsequent :dep
  lines. Thanks JohnScience!
• Reduced interleaving of stdout and stderr.
• Errors now render using ariadne, giving a much nicer presentation. Thanks
  HKalbasi!
• Small speedup in execution time by bypassing rustup.
• preserve_vars_on_panic is now true by default (as it used to be). It now
  works much better than before, with all variables being preserved if a panic
  occurs.
• By using rustyline's new external printer API, stderr output that hasn't been
  displayed before we return to the prompt no longer messes up the prompt. In
  fact, you can now spawn a thread that writes to stderr in the background and
  the output now appears above your prompt.
• Jupyter kernel now uses a native Rust library for ZMQ, so no longer requires
  cmake to build.
• The last bit of code that tried to use rustc error messages to determine
  variable types has been deleted. Now if rust-analyzer can't determine the type
  of a variable, we ask the user to add an explicit type annotation.
• Update rust-analyzer
• Building evcxr now requires rust 1.63 or higher.
• Added a release workflow so that binaries for the latest Linux (built on
  Ubuntu), Windows and Mac are available for download on the releases page.