Added a CSV example (#19318)

Co-authored-by: Joakim Sørensen <hi@ludeeus.dev>

source/_integrations/file.markdown

@@ -115,3 +115,30 @@ sensor:
 ```
 
 {% endraw %}
+
+#### Entries as CSV
+
+Assuming the log file contains multiple values formatted as CSV like shown below:
+
+```text
+timestamp,temperature,humidity
+1631472948,21,39
+1631472949,22,36
+```
+
+This would require the following entry in the `configuration.yaml` file to extract the temperature:
+
+{% raw %}
+
+```yaml
+# Example configuration.yaml entry
+sensor:
+  - platform: file
+    name: Temperature
+    file_path: /home/user/.homeassistant/sensor.csv
+    value_template: '{{ value.split(",")[1] }}'
+    unit_of_measurement: "°C"
+```
+
+{% endraw %}
+