Add horizontal rules before example sections (#1772)

Author: kaelig

src/components/AccountConnection/README.md

@@ -111,6 +111,8 @@ Connect to app
 
 <!-- end -->
 
+---
+
 ## Examples
 
 ### Default account connection

src/components/ActionList/README.md

@@ -76,6 +76,8 @@ Each item in an action list should be scannable avoiding unnecessary words and a
 
 <!-- end -->
 
+---
+
 ## Examples
 
 ### Action list in a popover

src/components/AppProvider/README.md

@@ -28,6 +28,8 @@ App provider is a required component that enables sharing global settings throug
 
 The app provider component is required to use Polaris. Without it, the components in your application will not function correctly. You must wrap the root (the top) of your application in the app provider component. We’ve created [several examples to show how that’s done](https://github.com/Shopify/polaris/blob/master/examples/README.md).
 
+---
+
 ## Examples
 
 ### Default

src/components/Avatar/README.md

@@ -47,6 +47,8 @@ image:
 - `alt="Business’s name"` if the avatar represents a business
 - `alt=""` if the name of the person/business appears next to the avatar as text
 
+---
+
 ## Examples
 
 ### Default avatar

src/components/Badge/README.md

@@ -68,6 +68,8 @@ Don’t use alternatives to existing badge options. Only create a new badge opti
 
 <!-- end -->
 
+---
+
 ## Examples
 
 ### Default badge

src/components/Banner/README.md

@@ -251,6 +251,8 @@ including packaging.
 
 <!-- end -->
 
+---
+
 ## Examples
 
 ### Default banners

src/components/Button/README.md

@@ -93,6 +93,8 @@ Add a menu item
 
 <!-- end -->
 
+---
+
 ## Examples
 
 ### Basic button

src/components/ButtonGroup/README.md

@@ -45,6 +45,8 @@ Button groups should:
 Follow the [content guidelines](/components/actions/button#content-guidelines)
 outlined in the button component.
 
+---
+
 ## Examples
 
 ### Default button group

src/components/CalloutCard/README.md

@@ -167,6 +167,8 @@ Add a menu item
 
 <!-- end -->
 
+---
+
 ## Examples
 
 ### Default callout card

src/components/Caption/README.md

@@ -53,6 +53,8 @@ Captions are primarily used in [data visualizations](/visuals/data-visualization
 
 <!-- end -->
 
+---
+
 ## Examples
 
 ### Default caption