Update README with new images

Author: lukeblevins

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 <h1>Files UWP</h1>
 <h3>Meet Files, a brand-new file manager for Windows 10.</h3>
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+<img src="Assets/FilesDrive.jpg" width="800px">
 <p>Created from the ground up to look and feel amazing, Files is built to replace the outdated Windows File Explorer.</p>
 <a href="https://youtu.be/1wSA8PYKhpA?t=124">Link to old sideloading help video</a>