Add docs for multiple dashboard and resources in yaml mode (#12332)

* Add docs for multiple dashboard and resources in yaml mode

* Update yaml-mode.markdown

* Update yaml-mode.markdown

* Update yaml-mode.markdown

* Update yaml-mode.markdown

* Update yaml-mode.markdown

* Update yaml-mode.markdown

source/lovelace/yaml-mode.markdown

@@ -23,8 +23,101 @@ When you make changes to `ui-lovelace.yaml`, you don't have to restart Home Assi
 
 To revert back to using the UI to edit your Lovelace interface, remove the `lovelace` section from your `configuration.yaml` and copy the contents of your `ui-lovelace.yaml` into the raw configuration section of Home Assistant and restart.
 
+### Advanced configuration
 
-As a super minimal example, here's the bare minimum you will need for this to work:
+You can define multiple dashboards that all have their own YAML file, and add custom resources that are shared by all dashboards.
+
+```yaml
+lovelace:
+  mode: yaml
+  # Include external resources only add when mode is yaml, otherwise manage in the resources in the lovelace configuration panel.
+  resources:
+    - url: /local/my-custom-card.js
+      type: module
+    - url: /local/my-webfont.css
+      type: css
+  # Add more dashboards
+  dashboards:
+    generated:
+      mode: yaml
+      filename: notexist.yaml
+      title: Generated
+      icon: mdi:tools
+      show_in_sidebar: true
+      require_admin: true
+    hidden:
+      mode: yaml
+      title: hidden
+      show_in_sidebar: false
+      filename: hidden.yaml
+```
+
+You can also add YAML dashboards when your main dashboard is UI configurated:
+```yaml
+lovelace:
+  mode: storage
+  # Add yaml dashboards
+  dashboards:
+    yaml:
+      mode: yaml
+      title: YAML
+      icon: mdi:script
+      show_in_sidebar: true
+      filename: lovelace.yaml
+```
+
+{% configuration Lovelace %}
+mode:
+  required: true
+  description: "In what mode should the main Lovelace panel be, `yaml` or `storage` (UI managed)."
+  type: string
+resources:
+  required: false
+  description: "List of resources that should be loaded when you use Lovelace. Only use this when mode is `yaml`."
+  type: list
+  keys:
+    url:
+      required: true
+      description: The URL of the resource to load.
+      type: string
+    type:
+      required: true
+      description: "The type of resource, this should be either `module` for a JavaScript module or `css` for a StyleSheet."
+      type: string
+dashboards:
+  required: false
+  description: Additional Lovelace YAML dashboards.
+  type: map
+  keys:
+    mode:
+      required: true
+      description: "The mode of the dashboard, this should always be `yaml`. Dashboards in `storage` mode can be created in the Lovelace configuration panel."
+      type: string
+    filename:
+      required: true
+      description: "The file in your `config` directory where the Lovelace configuration for this panel is."
+      type: string
+    title:
+      required: true
+      description: "The title of the dashboard, will be used in the sidebar."
+      type: string
+    icon:
+      required: false
+      description: The icon to show in the sidebar.
+      type: string
+    show_in_sidebar:
+      required: false
+      description: Should this view be shown in the sidebar.
+      type: boolean
+      default: true
+    require_admin:
+      required: false
+      description: Should this view be only accessible for admin users.
+      type: boolean
+      default: false
+{% endconfiguration %}
+
+As a super minimal example of a Lovelace dashboard config, here's the bare minimum you will need for it to work:
 
 ```yaml
 title: My Awesome Home
@@ -39,17 +132,10 @@ views:
           Welcome to your **Lovelace UI**.
 ```
 
-A slightly more advanced example shows additional elements which can be used to customize your frontend.
+A slightly more advanced example:
 
 ```yaml
 title: My Awesome Home
-# Include external resources
-resources:
-  - url: /local/my-custom-card.js
-    type: js
-  - url: /local/my-webfont.css
-    type: css
-
 views:
     # View tab title.
   - title: Example