README.md: added information about the engine modes, supported .NET types and simple example of usage

Author: Taritsyn

README.md

@@ -6,9 +6,79 @@ MSIE JavaScript Engine for .NET
 This project is a .NET wrapper for working with the Internet Explorer's JavaScript engines (JsRT version of Chakra, ActiveScript version of Chakra and Classic JavaScript Engine). 
 Project was based on the code of [SassAndCoffee.JavaScript](http://github.com/paulcbetts/SassAndCoffee) and [Chakra Sample Hosts](http://github.com/panopticoncentral/chakra-host).
 
+MSIE JavaScript Engine requires a installation of Internet Explorer on the machine and can work in 4 modes, that are defined in the `MsieJavaScriptEngine.JsEngineMode` enumeration:
+
+ * `Auto`. Automatically selects the most modern JavaScript engine from available on the machine.
+ * `Classic`. Classic MSIE JavaScript engine (supports ECMAScript 3 with possibility of using the ECMAScript 5 Polyfill and the JSON2 library). Requires Internet Explorer 6 or higher on the machine.
+ * `ChakraActiveScript`. ActiveScript version of Chakra JavaScript engine (supports ECMAScript 3 with possibility of using the ECMAScript 5 Polyfill and the JSON2 library). Requires Internet Explorer 9 or higher on the machine.
+ * `ChakraJsRt`. JsRT version of Chakra JavaScript engine (supports ECMAScript 5). Requires Internet Explorer 11 or higher on the machine. Detailed information about JsRT you can read in the [Paul Vick's blog](http://www.panopticoncentral.net/category/javascript/).
+
+The supported .NET types are as follows:
+
+ * `MsieJavaScriptEngine.Undefined`
+ * `System.Boolean`
+ * `System.Int32`
+ * `System.Double`
+ * `System.String`
+
 ## Installation
 This library can be installed through NuGet - [http://nuget.org/packages/MsieJavaScriptEngine](http://nuget.org/packages/MsieJavaScriptEngine).
 
+## Usage
+Consider a simple example of usage of the MSIE JavaScript Engine:
+
+	namespace MsieJavaScriptEngine.Example.Console
+	{
+		using System;
+
+		using MsieJavaScriptEngine;
+		using MsieJavaScriptEngine.Helpers;
+
+		class Program
+		{
+			static void Main(string[] args)
+			{
+				try
+				{
+					using (var jsEngine = new MsieJsEngine(engineMode: JsEngineMode.Auto, 
+						useEcmaScript5Polyfill: false, useJson2Library: false))
+					{
+						const string expression = "7 * 8 - 20";
+						var result = jsEngine.Evaluate<int>(expression);
+
+						Console.WriteLine("{0} = {1}", expression, result);
+					}
+				}
+				catch (JsEngineLoadException e)
+				{
+					Console.WriteLine("During loading of JavaScript engine an error occurred.");
+					Console.WriteLine();
+					Console.WriteLine(JsErrorHelpers.Format(e));
+				}
+				catch (JsRuntimeException e)
+				{
+					Console.WriteLine("During execution of JavaScript code an error occurred.");
+					Console.WriteLine();
+					Console.WriteLine(JsErrorHelpers.Format(e));
+				}
+
+				Console.ReadLine();
+			}
+		}
+	}
+
+First we create an instance of the `MsieJsEngine` class and pass the following parameters to the constructor:
+
+ 1. `engineMode` - JavaScript engine mode;
+ 2. `useEcmaScript5Polyfill` - flag for whether to use the ECMAScript 5 Polyfill;
+ 3. `useJson2Library` - flag for whether to use the [JSON2](http://github.com/douglascrockford/JSON-js) library.
+
+The values of constructor parameters in the above code correspond to the default values.
+
+Then we evaluate a JavaScript expression by using of the `Evaluate` method and output its result to the console.
+
+In addition, we provide handling of the following exception types: `JsEngineLoadException` and `JsRuntimeException`.
+
 ## Release History
 See the [changelog](CHANGELOG.md).