Readme - app & project presentation (#18)

* Add empty template for README

* Write a summary and explanation of the RNN app

* Write the Installation and usage of the RNN app

* Describe the architecture and include diagrams

* Use transparent diagrams for better Dark/Light theme experience

* Present the results - GIFs with app usage

Author: BartoszKlonowski

README.md

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+<h1 align="center"> ReactNativeNotes </h1>
+<p align="center">
+    Demo application to create and keep your notes and tasks.
+</p>
+
+This project is a demonstration application that should present the abilites and skills of [Callstack.io](https://callstack.com) company in creating React Native Windows **desktop** applications.
+
+The idea behind creating the Notes app was to include some features of Windows and React Native Windows [APIs](https://docs.microsoft.com/en-us/windows/uwp/cpp-and-winrt-apis/consume-apis) but also to create the application that will contain all the most common usage scenarios of an example desktop application.
+
+The development of this application was also a perfect opportunity to mix both React Native (JavaScript) development with the native UWP (C++) features.
+It means that beside standard React Native components there is a whole UWP layer which handles all the navigation, animations, and content of a Windows desktop app.
+Please check the [Approach](#Approach) section for more details.
+
+
+---
+  
+## Installation & Usage ##
+
+To play with this app
+* Make sure to meet all the [System requirements](https://microsoft.github.io/react-native-windows/docs/rnw-dependencies) for React Native Windows development
+* Clone the repository
+* Launch the terminal and start the app by the following command:
+```
+npx react-native run-windows --arch x64
+```
+(or add `--release --no-launch` to the command line to use the Release version)
+This will start all the required tools and launch your app
+* alternatively you can launch your app through the Visual Studio by opening the solution file in *\<repo root>/windows/ReactNativeNotes.sln* and launching the Debug configuration.
+
+
+---
+
+## Approach ##
+
+The following application is the combination of skills and features of React Native and UWP development.
+
+There are two main layers of the application:
+![](./Resources/GeneralArchitectureDiagramTransparent.PNG)
+
+The first is the UWP layer contains all the XAML Pages of the application.
+Those Pages can be navigated between using the [`NavigationView`](https://docs.microsoft.com/en-us/uwp/api/windows.ui.xaml.controls.navigationview?view=winrt-20348).
+
+Each Page can host exactly one separate `Component` implemented on the React Native side.
+These components acts as a View for the application.
+
+So in more details, the architecture looks like:
+![](./Resources/DetailedDiagramTransparent.png)
+
+So comparing to original React Native Windows where whole application starts from an `index.js` and `App.js`, this solution makes the UWP being a root hosting not an `index.js`, but many `Components`.
+
+
+
+---
+
+## Results ##
+
+The application contains two main screens:
+* Notes screen - where all the notes are available for all the Create/Read/Update/Delete operations:
+![](./Resources/README-notes-CRUD.gif)
+![](./Resources/README-notes-resize.gif)
+* Tasks screen - where all the tasks are available with calendar date picker for specifying the deadline of a task.
+![](./Resources/README-tasks.gif)
+