docs: update in this documentation section (#485)

Update the "In this documentation" section on the main page.

docs/index.md

@@ -12,21 +12,29 @@ Pebble is useful for developers who are building [Juju charms on Kubernetes](htt
 
 ````{grid} 1 1 2 2
 ```{grid-item-card} [Tutorial](tutorial/getting-started)
-**Start here**: a hands-on getting started introduction to Pebble for new users.
+**Start here**: a hands-on introduction to Pebble, guiding you through your first steps using the CLI
 ```
 
 ```{grid-item-card} [How-to guides](how-to/index)
-**Step-by-step guides** covering key operations and common tasks.
+**Step-by-step guides** covering key operations and common tasks
+- [Install Pebble](how-to/install-pebble)
+- [Manage service dependencies](how-to/service-dependencies)
+- [Manage identities](how-to/manage-identities)
 ```
 ````
 
 ````{grid} 1 1 2 2
 ```{grid-item-card} [Explanation](explanation/index)
-**Discussion and clarification** of key topics.
+**Discussion and clarification** of key topics
+- [General model](explanation/general-model.md)
+- [API and clients](explanation/api-and-clients.md)
 ```
 
 ```{grid-item-card} [Reference](reference/index)
-**Technical information** - specifications, APIs, and architecture.
+**Technical information**
+- [Layer specification](reference/layer-specification)
+- [CLI commands](reference/cli-commands/cli-commands)
+- [Pebble in containers](reference/pebble-in-containers)
 ```
 ````