docs(mdbook): Integrate README of signstar-config crate

Signed-off-by: David Runge <dvzrv@archlinux.org>

resources/docs/src/SUMMARY.md

@@ -15,6 +15,7 @@
 - [nethsm-tests](./nethsm-tests/README.md)
   - [CHANGELOG](./nethsm-tests/CHANGELOG.md)
 - [signstar-common](./signstar-common/README.md)
+- [signstar-config](./signstar-config/README.md)
 - [signstar-configure-build](./signstar-configure-build/README.md)
   - [CHANGELOG](./signstar-configure-build/CHANGELOG.md)
 - [signstar-request-signature](./signstar-request-signature/README.md)

resources/docs/src/signstar-config/README.md

+../../../../signstar-config/README.md
\ No newline at end of file