Add README.md

Installation instructions and some general troubleshooting steps.

README.md

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+# EdgeDeflector
+
+*EdgeDeflector* is  a small helper application that intercepts URIs that force-open web links in Microsoft Edge and redirects it to the system’s default web browser. This allows you to use Windows features like the Cortana assistant and built-in help links with the browser of your choice instead of being forced to use Microsoft Edge.
+
+You’ll never see EdgeDeflector ever again after installing it. It does its thing transparently in the background and only runs when a link needs to be deflected away from Microsoft Edge.
+
+System requirements: Windows 10, your favorite web browser
+
+# Installation
+
+  1. Download the latest version of EdgeDeflector.exe from [GitHub releases](https://github.com/da2x/EdgeDeflector/releases)
+  2. Copy the downloaded executable to `C:\Program Files\` or anywhere else it can be stored permanently
+  3. Run the program once to configure your system
+  4. Choose `EdgeDeflector` and `Always use this app` in the dialog
+
+You may need to repeat the above steps after installing major feature updates to Windows through Windows Update. You can subscribe to the [AppCast feed](https://github.com/da2x/EdgeDeflector/releases.atom) to be notified of any new releases.
+
+If you dismiss the dialog, or choose the wrong app; you can apply the change  in the Windows Settings  app: Apps: Default apps: Choose default apps by protocol: microsoft-edge.
+
+If EdgeDeflector isn’t listed in either locations, try running it one more time; or lastly restarting your PC before you try again. (This last option actually helps if the System Registry is locked up or Windows is being suborn.)
+
+You don’t need to specify your browser of choice in EdgeDeflector. It will pick up on the system configured default from Windows Settings app: Apps: Default apps: Web browser.