add mono instructions (#2121)

CONTRIBUTING.md

@@ -23,9 +23,9 @@ Articles are written in [DocFx-flavored Markdown](http://dotnet.github.io/docfx/
 
 For each Markdown file there may be a folder for images and a folder for sample code. For example, if the article is [fundamentals/configuration.md](https://github.com/aspnet/Docs/blob/master/aspnetcore/fundamentals/configuration.md), the images are in [fundamentals/configuration/\_static](https://github.com/aspnet/Docs/tree/master/aspnetcore/fundamentals/configuration/_static) and the sample application project files are in [fundamentals/configuration/sample](https://github.com/aspnet/Docs/tree/master/aspnetcore/fundamentals/configuration/sample).  An image in the *fundamentals/configuration.md* file is rendered by the following Markdown.
 
-````none
+```none
 ![alt-text](configuration/_static/imagename.png)
-````
+```
 
 ## Code snippets
 
@@ -35,42 +35,42 @@ Here are some examples of [DFM code snippet syntax](http://dotnet.github.io/docf
 
 To render an entire code file as a snippet:
 
-````none
+```none
 [!code-csharp[Main](configuration/sample/Program.cs)]
-````
+```
 
 To render a portion of a file as a snippet by using line numbers:
 
-````none
+```none
 [!code-csharp[Main](configuration/sample/Program.cs?range=1-10,20,30,40-50]
 [!code-html[Main](configuration/sample/Views/Home/Index.cshtml?range=1-10,20,30,40-50]
 [!code-javascript[Main](configuration/sample/Project.json?range=1-10,20,30,40-50]
-````
+```
 
 For C# snippets, you can reference a [C# region](https://msdn.microsoft.com/en-us/library/9a1ybwek.aspx). Whenever possible, use regions rather than line numbers, because line numbers in a code file tend to change and get out of sync with line number references in Markdown. C# regions can be nested, and if you reference the outer region, the inner `#region` and `#endregion` directives are not rendered in a snippet. 
 
 To render a C# region named "snippet_Example":
 
-````none
+```none
 [!code-csharp[Main](configuration/sample/Program.cs?name=snippet_Example)]
-````
+```
 
 To highlight selected lines in a rendered snippet (usually renders as yellow background color):
 
-````none
+```none
 [!code-csharp[Main](configuration/sample/Program.cs?name=snippet_Example&highlight=1-3,10,20-25)]
 [!code-csharp[Main](configuration/sample/Program.cs?range=10-20&highlight=1-3]
 [!code-html[Main](configuration/sample/Views/Home/Index.cshtml?range=10-20&highlight=1-3]
 [!code-javascript[Main](configuration/sample/Project.json?range=10-20&highlight=1-3]
-````
+```
 
 ## Test your changes with DocFX
 
-Test your changes with the [DocFX command line tool](https://dotnet.github.io/docfx/tutorial/docfx_getting_started.html#2-use-docfx-as-a-command-line-tool), which creates a locally hosted version of the site. 
+Test your changes with the [DocFX command line tool](https://dotnet.github.io/docfx/tutorial/docfx_getting_started.html#2-use-docfx-as-a-command-line-tool), which creates a locally hosted version of the site. DocFX doesn't render style and site extensions created for docs.microsoft.com.
 
-DocFX requires the .NET Framework on Windows, or Mono for Linux or macOS. DocFX doesn't render style and site extensions created for docs.microsoft.com.
+DocFX requires the .NET Framework on Windows, or Mono for Linux or macOS. 
 
-Follow these steps to build the site locally and view your changes:
+### Windows instructions
 
 * Download and unzip *docfx.zip* from [DocFX releases](https://github.com/dotnet/docfx/releases).
 * Add DocFX to your PATH.
@@ -82,6 +82,25 @@ Follow these steps to build the site locally and view your changes:
 
 * In a browser, navigate to `http://localhost:8080`.
 
+### Mono instructions
+
+* Install Mono via Homebrew - `brew install mono`.
+* Download the [latest version of DocFX](https://github.com/dotnet/docfx/releases/tag/v2.7.2).
+* Extract to `\bin\docfx`.
+* Create an alias for **docfx**:
+
+  ```
+  function docfx {
+    mono $HOME/bin/docfx/docfx.exe
+  }
+    
+  function docfx-serve {
+    mono $HOME/bin/docfx/docfx.exe serve _site
+  }
+  ```
+
+* Run **docfx** in the `Docs\aspnetcore` directory to build the site, and **docfx-serve** to view the site at `http://localhost:8080`.
+
 ## Voice and tone
 
 Our goal is to write documentation that is easily understandable by the widest possible audience. To that end we have established guidelines for writing style that we ask our contributors to follow. For more information, see [Voice and tone guidelines](https://github.com/dotnet/docs/blob/master/styleguide/voice-tone.md) in the .NET Core repo.