Documentation for Participant Config Includes

[KonradBkd]

Subject

Docs for include semantics of the SIL Kit participant configuration.

Instructions for review / testing

Proofreading of the following sections:

• configuration/configuration.html
• configuration/includes-configuration.html

Developer checklist (address before review)

• [ ] Changelog.md updated
• [ ] Prepared update for depending repositories
• [ ] Documentation updated (public API changes only)
• [ ] API docstrings updated (public API changes only)
• [ ] Rebase → commit history clean
• [ ] Squash and merge → proper PR title