fix: add alignment option to home layout (#896)

This adds a configuration parameter for the home page layout to align
the content.

```toml
[params.ananke.home]
content_alignment = "center"
```

Default is `center` (due to it being the previous layout option).
Possible options are `left`, `right`, and `center`. This influences
_only_ the home page markdown content, not other parts of the home page.

---------

Signed-off-by: Patrick Kollitsch <83281+davidsneighbour@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>