Adds docs for folder_watcher component (#4885)

* Create folder_watcher.markdown

* Adds posting file

* Update folder_watcher.markdown

* ✏️ Markdownlint fixes

* ✏️ Escapes jinja code in example

* ✏️ Build fix part 2

* 🚑 Fixes build

* ⬆️ Ups ha_release to 0.67

source/_components/folder_watcher.markdown

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+---
+layout: page
+title: "folder watcher"
+description: "Component for monitoring changes within the filesystem."
+date: 2018-03-11 14:00
+sidebar: true
+comments: false
+sharing: true
+footer: true
+logo: home-assistant.png
+ha_category: System Monitor
+ha_iot_class: "Local Polling"
+ha_release: 0.67
+---
+
+This component adds [Watchdog](https://pythonhosted.org/watchdog/) file system monitoring, publishing events on the Home-Assistant bus on the creation/deletion/modification of files.
+
+To configure the `folder_watcher` component add to you `configuration.yaml` file:
+
+```yaml
+{% raw %}
+folder_watcher:
+  watchers:
+    - folder: /config
+{% endraw %}
+```
+
+{% configuration %}
+folder:
+  description: The folder path
+  required: true
+  type: string
+patterns:
+  description: Pattern matching to apply
+  required: false
+  default: "*" 
+  type: string
+{% endconfiguration %}
+
+## Patterns
+
+Pattern matching using [fnmatch](https://docs.python.org/3.6/library/fnmatch.html) can be used to limit filesystem monitoring to only files which match the configured patterns. The following example shows the configuration required to only monitor filetypes `.yaml` and `.txt`.
+
+```yaml
+{% raw %}
+folder_watcher:
+  watchers:
+    - folder: /config
+      patterns:
+        - '*.yaml'
+        - '*.txt'
+{% raw %}
+```
+
+## Automations
+
+Automations can be triggered on filesystem event data using a data_template. The following automation will send a notification with the name and folder of new files added to that folder:
+
+```yaml
+{% raw %}
+- action:
+  - data_template:
+      message: 'Created {{trigger.event.data.file}} in {{trigger.event.data.folder}}'
+      title: New image captured!
+      data:
+        file: "{{trigger.event.data.path}}"
+    service: notify.pushbullet
+  alias: New file alert
+  condition: []
+  id: '1520092824697'
+  trigger:
+  - event_data: {"event_type":"created"}
+    event_type: folder_watcher
+    platform: event
+{% endraw %}
+```
+