[Docs] Copy to clipboard functionality copies prompt characters

The tutorial has a nice copy to clipboard functionality, but unfortunately when you use it it copies the prompt characters like `$` and `>`

Should the code snippets maybe be changed to not include those characters, or the copy functionality modified to not copy them?

```
$ stack repl --package beam-core --package beam-sqlite --package sqlite-simple
```

```
> :set -XDeriveGeneric -XGADTs -XOverloadedStrings -XFlexibleContexts -XFlexibleInstances -XTypeFamilies -XTypeApplications
```