feat(ref): add appliance configuration options

reference/appliance-configuration.md

@@ -0,0 +1,20 @@
+(ref-appliance-configuration)=
+# Anbox Cloud Appliance configuration
+
+The Anbox Cloud Appliance provides various configuration items to customise its behaviour. Currently set configuration can be seen by running
+
+    sudo anbox-cloud-appliance config show
+
+Available configuration items can be changed by using the following command
+
+    sudo anbox-cloud-appliance config set <key>=<value> ...
+
+The following table lists the available configuration items and their meaning.
+
+| Name<br/>*(Type, Default)* | Description           |
+|-----|-----------------------|
+| `network.public_address`<br/>*(string, N/A)* | Public address (if behind NAT) of the machine the appliance is running on |
+| `network.location`<br/>*(string, N/A)* | DNS name used to access the appliance |
+| `core.https_allowed_origin`<br/>*(string, N/A)* | `Access-Control-Allow-Origin` HTTP header value for the reverse proxy of the appliance |
+| `core.https_allowed_headers`<br/>*(string, N/A)* | `Access-Control-Allow-Headers` HTTP header value for the reverse proxy of the appliance |
+| `core.https_allowed_methods`<br/>*(string, N/A)* | `Access-Control-Allow-Methods` HTTP header value for the reverse proxy of the appliance |

reference/landing.md

@@ -77,6 +77,7 @@ addon-manifest
 ams-configuration
 Anbox Cloud images <provided-images>
 appliance-preseed
+appliance-configurtation
 sdks
 api-reference
 application-manifest