Adds documentation for scheduled task mixin

docs/extend/plugins/schedule.md

@@ -5,3 +5,47 @@ title: Schedule Mixin
 ## ScheduleMixin
 
 The ScheduleMixin class provides a plugin with the ability to call functions at regular intervals.
+
+- Functions are registered with the InvenTree worker which runs as a background process.
+- Scheduled functions do not accept any arguments
+- Plugin member functions can be called
+- Global functions can be specified using dotted notation
+
+### Example
+
+An example of a plugin which supports scheduled tasks:
+
+```python
+class ScheduledTaskPlugin(ScheduleMixin, SettingsMixin, IntegrationPluginBase):
+    """
+    Sample plugin which runs a scheduled task, and provides user configuration.
+    """
+
+    PLUGIN_NAME = "Scheduled Tasks"
+    PLUGIN_SLUG = 'schedule'
+
+    SCHEDULED_TASKS = {
+        'global': {
+            'func': 'some_module.function',
+            'schedule': 'H',  # Run every hour
+        },
+        'member': {
+            'func': 'foo',
+            'schedule': 'I',  # Minutes
+            'minutes': 15,
+        },
+    }
+
+    SETTINGS = {
+        'SECRET': {
+            'name': 'A secret',
+            'description': 'User configurable value',        
+        },    
+    }
+
+    def foo(self):
+        """
+        This function runs every 15 minutes
+        """
+        secret_value = self.get_setting('SECRET')
+        print(f"foo - SECRET = {secret_value})