Use standard syntax for output codeblocks.

[johnnymatthews]

Writers can now use the following syntax when creating codeblocks that only contain output:

1. Install something:

```shell
sudo apt install something -y
```

```output
whatever_apt_outputs_when_installing_something
idk_i_cant_remember
```

This'll render the output block, but in black and white (no syntax highlighting) and no copy button. The idea here is to make it easier for readers to see what should and should not be copied into their terminal.

It looks like this:

Essentially a re-creation of #151, but this time for the Zola site (last one was Docusaurus).