[doc] Automate examples doc creation
The example READMEs currently have to be created with the `bin/merge_cpp_and_md.sh` script AFAIK.
To execute the script you need to correct files and the correct file order. However I couldn't find the specific command for each example being documented anywhere.
Maybe we could create something like a `.doc_config` that lists this information for each example?
Then it would be also easy to create a script that builds all examples docs
issue