std::io::Write import
Replace r_println!/r_print! macro usage across all example renderers
with
explicit RenderResult construction using std::io::Write, enabling more
flexible output handling and reducing reliance on macro-side effects.
Add a new example demonstrating global resource injection in chain
functions,
and update all existing examples to import from `mingling::prelude`
instead
of individual macro paths. Also add `example-resources` to the workspace
exclude list.
