add license credits

docs/credits.md

@@ -0,0 +1,13 @@
+While the Mobile.BuildTools does not add any external dependencies to your projects, we could not do what we do without being able to build on the hard work from other projects. Though the Mobile.BuildTools is licensed under the MIT License, some of our dependencies use alternate Open Source licenses.
+
+| Project | License | GitHub |
+|:-------:|:-------:|:------:|
+| MSBuild | MIT | [microsoft/msbuild](https://github.com/microsoft/msbuild) |
+| Newtonsoft.Json | MIT | [JamesNK/Newtonsoft.Json](https://github.com/JamesNK/Newtonsoft.Json) |
+| SharpScss | BSD 2 | [xoofx/SharpScss](https://github.com/xoofx/SharpScss) |
+| NUglify | BSD 2 | [xoofx/NUglify](https://github.com/xoofx/NUglify) |
+| Microsoft.Web.Xdt* | Apache | [aspnet/xdt](https://github.com/aspnet/xdt) |
+| SixLabors.ImageSharp | Apache | [SixLabors/ImageSharp/](https://github.com/SixLabors/ImageSharp/) |
+
+!!!! note Note
+    Microsoft.Web.Xdt is the only reference added to projects, if using the Mobile.BuildTools.Configuration pacakge. There is never any bloat added by the core Mobile.BuildTools pacakge to your applications.

mkdocs.yml

@@ -90,5 +90,6 @@ nav:
     - Appendix:
       - Upgrading from 1.X: appendix/upgrade.md
       - Apple Push Notifications: appendix/aps.md
+    - Credits: credits.md
 
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