Docs: fix budgets story (angular#12585)

* docs: fix typo in budgets story

* docs: add example in budgets story

Author: nlm-pro

docs/documentation/stories/budgets.md

@@ -4,7 +4,7 @@
 
 As applications grow in functionality, they also grow in size. Budgets is a feature in the
 Angular CLI which allows you to set budget thresholds in your configuration to ensure parts
-of your application stay within boundries which you set.
+of your application stay within boundaries which you set.
 
 **angular.json**
 ```
@@ -62,3 +62,24 @@ Available formats:
 
 All sizes are relative to baseline.
 Percentages are not valid for baseline values.
+
+## Example
+
+```
+{
+  ...
+  "configurations": {
+    "production": {
+      ...
+      budgets: [
+        {
+          "type": "bundle",
+          "name": "vendor",
+          "minimumWarning": "300kb",
+          "minimumError": "400kb",
+        }
+      ]
+    }
+  }
+}
+```