Should we keep the GHC error message as a separate file?

In the examples for each error message we currently have the following directory structure:
```
- before/module.hs
- after/module.hs
- index.md
```

and the `index.md` looks something like this:

```
---
title: Interesting description
---

Blablabla

Main.hs:4:1: error: [GHC-44432]
The type signature for ‘foo’ lacks an accompanying binding
|
4 | foo :: Int
| ^^^
```

Should we maybe think about moving the error message into a separate file? Maybe like the following:

```
- before/module.hs
- after/module.hs
- index.md
- error.stderr
```

And then use Hakyll to insert the error message into the description?
The main motivation is that it will be much more difficult to do anything with scripts which could regenerate or check the error output in the future. Opinions: @david-christiansen ?