Allow multiline formatting of examples in the docs

[sbarzowski]

Some stdlib functions like std.manifestTomlEx and std.manifestJsonMinified would benefit from multi-line presentation of examples.

We still want to keep the definitions semantic (we should avoid explicit multiline option). Perhaps we can auto-detect if it has multiple lines and use different formatting then (pre vs code).

In the long term, they should be interactive anyway (but we need to have a more compact way to present them visually).