Adds Fliplet.Widget.find() docs

docs/API/core/widget.md

@@ -2,6 +2,22 @@
 
 ## Core widget APIs
 
+### Find widgets for a page
+
+```js
+Fliplet.Widget.find().then(function(instances) {
+  // Returns all widget instances for a page
+});
+
+Fliplet.Widget.find({ package: 'com.fiplet.image' }).then(function(instances) {
+  // Returns all image widget instances for a page
+});
+
+Fliplet.Widget.findOne({ package: 'com.fiplet.image' }).then(function(instance) {
+  // Returns the first image widget instance found on a page
+});
+```
+
 ### Get the JSON schema of a widget
 
 You can use this method to fetch the JSON schema of a widget. The following widget packages are currently supporting this feature: