The optaplanner manual (blue button on optaplanner.org) chapter 3 describes all examples, including all hard, medium and soft constraints of each example.

For the conference scheduling examples, that's in this asciidoc file:
https://github.com/kiegroup/optaplanner/blob/master/optaplanner-docs/src/main/asciidoc/UseCasesAndExamples/ConferenceScheduling/ConferenceScheduling-section.adoc
Please update that file.

to build the docs too, build with "mvn clean install -Dfull" (or just "cd optaplanner-docs" first). You'll find the html and pdf in optaplanner-docs/target/...

To learn asciidoc, I warmly recommend https://asciidoctor.org/docs/asciidoc-syntax-quick-reference/ and the intellij plugin for asciidoc(tor)