Update README with initial content

Author: jonwis

README.md

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+# Project Reunion
+
+Project Reunion provides functionality that supports all your apps on Windows.
+
+## Roadmap
+
+We're following a [roadmap](docs/roadmap.md) that gets us to building a v1.0 of Reunion exploring
+some basic common features.  You can help by filing issues for features you'd like to see!
+
+## Documentation
+
+* [Roadmap](docs/roadmap.md) - where we're going
+* [High-level overview](docs/overview.md) - why we're doing this, how you can use it
+* [Using Reunion](docs/developer-guide.md) - how to use Reunion in your app
+* [Contributor/developer Guide](docs/contributor-guide.md) - how to contribute to Reunion
+* [Implementation/API design Guide](docs/implementation-guide.md) - how to define and implement
+  Reunion components.
+* [FAQ](docs/faq.md) - frequently asked questions about Project Reunion
+
+## Features
+
+### Benefits
+
+_Windows and Reunion loves all your apps_
+
+The Reunion Framework helps you use modern features of Windows across all your apps, across all your
+users. You'll get access to modern features of the Windows Application Platform at your own pace.
+Improve power use and uphold privacy requirements in your existing apps.  Update your app to use
+APIs that automatically switch to fill-in support on older versions of Windows.  Get access to
+more of Windows from your UWPs. Connect to notifications from your Win32 applications.
+
+1. Reunion stays up to date automatically as new versions are available without recompilation or
+updates to your app.
+
+2. Reunion APIs are backwards-compatible across a range of Windows versions and provide a clear
+message to you that an API might not be supported.
+
+3. Reunion works for packaged, unpackaged, UWP, Desktop Bridge, and bring-your-own identity apps.
+Write your app or framework code once and use it everywhere.
+
+4. Reunion helps you incrementally adopt powerful Windows features like AppContainer, Desktop
+Bridge, Identity, and more.
+
+### API Support
+
+Reunion supports many of the APIs in Windows already. See below for a list and links to both
+definition and sample code.
+
+| Area          | Description                                                   | IDL | Sample |
+| ------------- | ------------------------------------------------------------- | --- | ------ |
+| Startup Tasks | Schedule your app to run when the user logs in                |     |        |
+| App Lifecycle | Events tracking app start & stop requests, login/out, restart |     |        |
+| Storage       | Store your app's data in a central location per user          |     |        |
+
+
+### Version Support
+
+At this time, Reunion supports Windows `TargetPlatformVersion` >= 10.0.18362 (Windows 10 1809) or
+greater. 
+
+Your app's users can be on any of the following supported Windows 10 versions:
+
+* Windows Insider Previews
+* May 2019 Update (18362 aka "19H1")
+* October 2018 Update (17763 aka "Redstone 5")
+* April 2018 Update (17134 aka "Redstone 4")
+* Fall Creators Update (16299 aka "Redstone 3")
+
+When features have partial implementations on older versions of Windows they will have an
+[`IsSupported`](docs/developer-guide.md) method indicating what level of support is present.
+
+## Data/Telemetry
+
+This project collects usage data and sends it to Microsoft to help improve our products and services. See the [privacy statement](privacy.md) for more details.
+
+For more information on telemetry implementation see the [developer guide](docs/developer-guide.md#Telemetry).
+
+# Quick Start
+
+## Using Reunion in Your Apps
+
+There are [multiple samples available](samples/README.md). Briefly the steps are:
+
+1. [Add a reference](docs/developer-guide.md#Packages) to the Microsoft.Reunion package
+2. [Update your code](docs/developer-guide.md#UpdateYourApp) to use Reunion functionality
+3. [Deploy your app](docs/developer-guide.md#DeployingReunion) with Reunion
+
+## Requesting Reunion Functionality
+
+File a [new issue!](https://github.com/microsoft/ProjectReunion/issues/new/choose) Tell us what problem you're
+trying to solve, how you've tried to solve it so far, and what would be the ideal solution for your app.  Bonus
+points if there's a gist or existing repo we can look at with you.  There's [a fuller description](docs/expanding-reunion.md)
+of how this works, how you & the community can help, and more available.
+
+## Contributing to Union
+
+First, read the [Contributing](#Contributing) section.  Then:
+
+1. Create a fork of this repo then clone it
+1. Start Visual Studio 2019 on [ProjectReunion.sln](./ProjectReunion.sln)
+1. [Modify the code](docs/implementation.md#UpdatingReunion) you'd like to see changed
+1. [Add tests](docs/implementation.md#Testing) for your fix or functionality
+1. [Create a pull request](docs/implementation.md#PullRequest) from your fork to this repo
 
 # Contributing