Fix How-to-use-post-processing.html typo

docs/manual/en/introduction/How-to-use-post-processing.html

@@ -24,7 +24,7 @@
 		<h2>Workflow</h2>
 
 		<p>
-			The first step in the process is to import all necessary files from the examples directory. The guide assumes your are using the official
+			The first step in the process is to import all necessary files from the examples directory. The guide assumes you are using the official
 			[link:https://www.npmjs.com/package/three npm package] of three.js. For our basic demo in this guide we need the following files.
 		</p>