message: docs: Consistently capitalise `Cargo`
diff: @@ -28,7 +28,7 @@ After cloning, you can now run the [REPL][repl-wikipedia] using Cargo:
  cargo run repl
  ```
  -You will now need to wait for cargo to download and build the dependencies, but
  +You will now need to wait for Cargo to download and build the dependencies, but
  sooner or later the REPL will be ready for you to interact with!
  [repl-wikipedia]: https://en.wikipedia.org/wiki/Read%E2%80%93eval%E2%80%93print_loop
  