Add custom holidays to workday sensor (#8887)

* Add custom holidays to workday sensor

* Keep configuration sample minimal

source/_components/binary_sensor.workday.markdown

@@ -30,7 +30,6 @@ To enable the `workday` sensor in your installation, add the following to your `
 binary_sensor:
   - platform: workday
     country: DE
-    workdays: [mon, wed, fri]
 ```
 
 {% configuration %}
@@ -63,11 +62,14 @@ days_offset:
   required: false
   type: integer
   default: 0
+add_holidays:
+  description: "Add custom holidays (such as company, personal holidays or vacations). Needs to formatted as `YYYY-MM-DD`." 
+  required: false
+  type: list
 {% endconfiguration %}
 
 Days are specified as follows: `mon`, `tue`, `wed`, `thu`, `fri`, `sat`, `sun`.
-The keyword `holiday` is used for public
+The keyword `holiday` is used for public holidays identified by the holidays module.
-holidays identified by the holidays module.
 
 <p class='note warning'>
 If you use the sensor for Norway (`NO`) you need to wrap `NO` in quotes or write the name in full.
@@ -76,6 +78,22 @@ If you use the sensor for Canada (`CA`) with Ontario (`ON`) as `province:` then
 Otherwise the value is evaluated as `true` (check the YAML documentation for further details) and the sensor will not work.
 </p>
 
+## {% linkable_title Full example %}
+
+This examples excludes Saturdays, Sundays and holiday. Two custom holidays are added.
+
+```yaml
+# Example configuration.yaml entry
+binary_sensor:
+  - platform: workday
+    country: DE
+    workdays: [mon, wed, fri]
+    excludes: [sat, sun, holiday]
+    add_holidays: 
+      - '2018-12-26'
+      - '2018-12-31'
+```
+
 ## {% linkable_title Automation example %}
 
 Example usage for automation:
@@ -98,4 +116,3 @@ automation:
 <p class='note'>
 Please remember that [as explained here](/docs/configuration/devices/) you can only have a single `automation:` entry. Add the automation to your existing automations.
 </p>
-