Add pictures and improve attributes for device for Juniper MX204 (#2031)

* feat: Add pictures for device Juniper MX204

Add elevation-images for device Juniper MX204.

* fix: Fixed weight for device Juniper MX204

* feat: Added comment with link to data sheet for Juniper MX204

device-types/Juniper/MX204.yaml

@@ -4,11 +4,13 @@ model: MX204
 slug: juniper-mx204
 part_number: MX204
 u_height: 1
-weight: 7.71
+weight: 10.5
 weight_unit: kg
-is_full_depth: false
-is_powered: true
 airflow: front-to-rear
+front_image: true
+rear_image: true
+is_full_depth: false
+comments: '[Juniper MX204 Data Sheet](https://www.juniper.net/content/dam/www/assets/datasheets/us/en/routers/mx-204-240-480-960-series-universal-routing-platforms-datasheet.pdf)'
 interfaces:
   - name: fxp0
     type: 1000base-t