feat: add docs about integration app knx

Description

[ ] the pull request title describes what this PR does (not a vague title like Update readme.md)
[ ] the pull request targets the default branch of the repository (develop)
[ ] the code follows the established code style of the repository, such as:
- npm run prettier:check passes
- npm run eslint:check passes
[ ] tests are added for the changes I made (if any source code was modified)
[ ] documentation added or updated
[ ] I have run the project locally and verified that there are no errors

fixes #[issue number], fixes #[issue number]