Added 'availability_template' to all Template Switch platform (#10310)

* Added 'availability_template' to all Template Swicth platform

* Fixed Syntax and default

* Removed optional parameter from example config

* Apply suggestions from code review

Co-Authored-By: Franck Nijhof <frenck@frenck.nl>

source/_integrations/switch.template.markdown

@@ -20,6 +20,7 @@ This can simplify the GUI and make it easier to write automations. You can mark
 To enable Template Switches in your installation, add the following to your `configuration.yaml` file:
 
 {% raw %}
+
 ```yaml
 # Example configuration.yaml entry
 switch:
@@ -36,6 +37,7 @@ switch:
           data:
             entity_id: switch.skylight_close
 ```
+
 {% endraw %}
 
 {% configuration %}
@@ -56,6 +58,11 @@ switch:
         description: Defines a template to set the state of the switch.
         required: true
         type: template
+      availability_template:
+        description: Defines a template to get the `available` state of the component. If the template returns `true`, the device is `available`. If the template returns any other value, the device will be `unavailable`. If `availability_template` is not configured, the component will always be `available`.
+        required: false
+        type: template
+        default: true
       turn_on:
         description: Defines an action to run when the switch is turned on.
         required: true
@@ -87,6 +94,7 @@ In this section you find some real-life examples of how to use this switch.
 This example shows a switch that copies another switch.
 
 {% raw %}
+
 ```yaml
 switch:
   - platform: template
@@ -102,6 +110,7 @@ switch:
           data:
             entity_id: switch.source
 ```
+
 {% endraw %}
 
 ### Toggle Switch
@@ -109,6 +118,7 @@ switch:
 This example shows a switch that takes its state from a sensor and toggles a switch.
 
 {% raw %}
+
 ```yaml
 switch:
   - platform: template
@@ -125,6 +135,7 @@ switch:
           data:
             entity_id: switch.blind_toggle
 ```
+
 {% endraw %}
 
 ### Sensor and Two Switches
@@ -133,6 +144,7 @@ This example shows a switch that takes its state from a sensor, and uses two
 momentary switches to control a device.
 
 {% raw %}
+
 ```yaml
 switch:
   - platform: template
@@ -149,6 +161,7 @@ switch:
           data:
             entity_id: switch.skylight_close
 ```
+
 {% endraw %}
 
 ### Change The Icon
@@ -156,6 +169,7 @@ switch:
 This example shows how to change the icon based on the day/night cycle.
 
 {% raw %}
+
 ```yaml
 switch:
   - platform: template
@@ -177,6 +191,7 @@ switch:
             mdi:garage
           {% endif %}
 ```
+
 {% endraw %}
 
 ### Change The Entity Picture
@@ -184,6 +199,7 @@ switch:
 This example shows how to change the entity picture based on the day/night cycle.
 
 {% raw %}
+
 ```yaml
 switch:
   - platform: template
@@ -205,4 +221,5 @@ switch:
             /local/garage-closed.png
           {% endif %}
 ```
+
 {% endraw %}