device management: update landing page

* Change file-name to match the desired slug
* Update the summary each service

Signed-off-by: Mike Szczys <mike@golioth.io>

Author: szczys

docs/device-management/1-home.md

@@ -0,0 +1,16 @@
+---
+title: Device Management
+sidebar_position: 0
+---
+
+Device Management encompasses all of the services that allow you to control your
+IoT fleet while it is in the field.
+
+* Control how OTA firmware updates are rolled out
+* Gather useful troubleshooting information using remote logging
+* Adjust how devices are functioning using the settings service
+* Issue device-specific commands using remote procedure calls
+
+Get familiar with Device Management via the Golioth web console. Then go beyond,
+using our REST API which provides access to everything available on the web
+console, plus additional functionality.