Docs: align how-to index with nav order

Author: xsedla1o

docs/howto/index.md

@@ -5,8 +5,9 @@ These guides walk through common DP³ application-development tasks step by step
 ## Available guides
 
 - [Get started with local DP³ app development](get-started.md) - Set up a local application environment for testing configuration, inputs, and modules before deploying them.
-- [How to deploy a DP³ application](deploy-app.md) - Install the backing services, generate the process-manager setup, and operate a live deployment.
-- [How to set up for DP³ platform development](develop-dp3.md) - Prepare the repository for working on DP³ itself, including tests and docs.
 - [How to add an attribute](add-attribute.md) - Define a new attribute in `db_entities`, roll the configuration out, send test data, and verify that DP³ accepts it.
 - [How to add an input module](add-input.md) - Connect an external producer to the DP³ API and verify that the incoming data is accepted.
 - [How to add a secondary module](add-module.md) - Add worker-side logic that reacts to incoming or stored data and emits derived results.
+- [How to deploy a DP³ application](deploy-app.md) - Install the backing services, generate the process-manager setup, and operate a live deployment.
+- [How to set up for DP³ platform development](develop-dp3.md) - Prepare the repository for working on DP³ itself, including tests and docs.
+- [How to extend the documentation](extending.md) - Build the docs locally, preview changes, and work with the documentation toolchain.