Write guidelines of use of$ in bash/console commands

[ncclementi]

In our docs we have multiple places where we have $ in front of a bash command and in others we don't. When present it's not copied when either selecting and using the copy to clipboard shortcut. But the $ will cause problems in multi line commands. This was fixed across the docs I believe, but we should write this as a guideline for future reference.

I would prefer we don't use it at all for simplicity, but this is a problem when we have a one liner with an output. For example:

```bash
$ echo $PATH
/some/path
```

In our docs, when you copy the cell above, you'll get only the one line that has $.

The one thing it's not clear is when we use console and when we use bash or if it doesn't matter. Ideally we should be consistent too.

TODO:

• Decide weather to use $ only having one liners and displaying the output, or not use it and modify across the docs
• Determine when we use console vs bash and if they are the same, choose one for consistency
• Write guidelines in the README under the "Writing" section.