Move lua files inside a user sub-directory

Apparently, this namespaces the lua files so you're doing

```
require('user.options')
```

instead of

```
--  this can be ambiguous in lua (?)
require('options')
```

I got this tip from https://youtu.be/hY5-Q6NxQgY but this tracks in what I'm seeing in many (but not all) other repos