Add docs for Ridwell (#19741)

Co-authored-by: Franck Nijhof <git@frenck.dev>

source/_integrations/ridwell.markdown

@@ -0,0 +1,65 @@
+---
+title: Ridwell
+description: Instructions on how to set up the Ridwell
+ha_category:
+  - Sensor
+ha_release: 2021.12
+ha_iot_class: Cloud Polling
+ha_domain: ridwell
+ha_codeowners:
+  - '@bachya'
+ha_config_flow: true
+ha_platforms:
+  - sensor
+---
+
+The Ridwell integration allows users to track waste recycling pickups scheduled with [Ridwell](https://www.ridwell.com).
+
+{% include integrations/config_flow.md %}
+
+## Pickup Types
+
+The pickup sensor contains a `pickup_types` state attribute, which contains:
+
+* The items being picked up during this particular event
+* The category of each item
+* The quantity of each item
+
+For example:
+
+```json
+{
+  "Latex Paint": {
+    "category": "add_on",
+    "quantity": 7
+  },
+  "Beyond the Bin": {
+    "category": "add_on",
+    "quantity": 2
+  },
+  "Fluorescent Light Tubes": {
+    "category": "add_on",
+    "quantity": 1
+  },
+  "Winter Coats and Jackets": {
+    "category": "rotating",
+    "quantity": 1
+  },
+  "Light Bulbs": {
+    "category": "standard",
+    "quantity": 1
+  },
+  "Batteries": {
+    "category": "standard",
+    "quantity": 1
+  },
+  "Threads": {
+    "category": "standard",
+    "quantity": 1
+  },
+  "Plastic Film": {
+    "category": "standard",
+    "quantity": 1
+  }
+}
+```