Previously, `layouts/_default/index.html` was referencing `.Params.framed`,
which looks for the `framed` parameter in the local document metadata,
rather than in the site configuration.
This commit replaces it with `$.Site.Params.framed`, allowing you to frame
the index content by setting in `config.toml`:
```
[params]
framed = true
```
ac8b097d82