chore: add playground examples codegen docs

.docs/PLAYGROUND_EXAMPLES.md

@@ -0,0 +1,23 @@
+# Playground examples docs
+
+This docs contains information to manage playground examples.
+
+## Modify playground examples
+
+To add, update or remove a playground example edit the [playground-examples.yaml](../playground-examples.yaml) file.
+
+This file contains two nested maps, first level is the example category and second level is example name:
+
+```yaml
+example category 1:
+    example name 1:
+        policy: path/to/policy/file (yaml or json)
+        payload: path/to/payload/file (yaml or json)
+    example name 2:
+        policy: path/to/policy/file (yaml or json)
+        payload: path/to/payload/file (yaml or json)
+example category 2:
+    # ...
+```
+
+Once the file edited, run `make codegen-playground-examples` to update the [data.json](../website/playground/assets/data.json) file.