Update README.md to include OS version numbers

Author: lukeblevins

README.md

@@ -5,7 +5,7 @@
 <p>Created from the ground up to look and feel amazing, Files is built to replace the outdated Windows File Explorer.</p>
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 <h3>Download Files</h3>
-<p>Files will eventually be available in the Microsoft Store, but you can <a href="https://drive.google.com/drive/folders/1cXCNPNoJWLj59lBV0SPxb5x3HYjphOFy?usp=sharing">download</a> a precompiled sideload package. Please note: these builds are unstable, incomplete, and only work on version <b>1803</b>. If you discover a bug, please fill out the form at <a href="https://goo.gl/forms/Z4bfKhaJJ6lT3Tcu2">this link</a>.</p> 
+<p>Files will eventually be available in the Microsoft Store, but you can <a href="https://drive.google.com/drive/folders/1cXCNPNoJWLj59lBV0SPxb5x3HYjphOFy?usp=sharing">download</a> a precompiled sideload package. Please note: these builds are unstable, incomplete, and only work on versions <b>1803 and 1809</b>. If you discover a bug, please fill out the form at <a href="https://goo.gl/forms/Z4bfKhaJJ6lT3Tcu2">this link</a>.</p> 
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 <img src="Assets/FeatureMap_Files.png" width="800px">