Add example implementing filter pushdown #21145
Description
Is your feature request related to a problem or challenge?
@pgwhalen says on https://github.com/apache/datafusion-site/pull/161/changes#r2972139725
As someone who struggled with implementing filter pushdown in a custom table provider before, it would be helpful if there was a section with examples on actually implementing it, just to specifying that the table provider supports it. Going from filters: &[Expr] to something more useful was pretty intimidating for me as a newbie. I ended up learning about LiteralGuarantee::analyze from the pruning_predicate.rs example and that was the big unlock, but as someone not familiar with database internals terminology, it was nonobvious initially.
Describe the solution you'd like
It would be cool to add an example that shows how to use PruningPredicate and LiteralGuarantee to decide among files based on predicates, for example
Describe alternatives you've considered
No response
Additional context
No response