Use Geoffrey to test rust code examples in markdown

## (Code) Example Of Cumbersome API

Currently, it can happen that due to some API adjustments code examples in the markdown files are no longer running. The [Geoffrey](https://github.com/ekxide/geoffrey) solves this problem.

## Improvement Suggestion

Only provide code examples in combination with geoffrey in markdown files.

The issue names no files; start by locating the Rust code examples in the repository's markdown files and read Geoffrey's documentation. Determine how the examples can be checked with Geoffrey, then verify that the markdown examples are covered and remain runnable.

Written by the indexing model from the issue text.