Fix mistake in integrating-with-other-libraries.md

The word "applications" is plural so it should be referred to with "them" instead of "it".

content/docs/integrating-with-other-libraries.md

@@ -194,7 +194,7 @@ React can be embedded into other applications thanks to the flexibility of [`Rea
 
 Although React is commonly used at startup to load a single root React component into the DOM, `ReactDOM.render()` can also be called multiple times for independent parts of the UI which can be as small as a button, or as large as an app.
 
-In fact, this is exactly how React is used at Facebook. This lets us write applications in React piece by piece, and combine it with our existing server-generated templates and other client-side code.
+In fact, this is exactly how React is used at Facebook. This lets us write applications in React piece by piece, and combine them with our existing server-generated templates and other client-side code.
 
 ### Replacing String-Based Rendering with React