Changed master to main in the links.

Author: dlemstra

.github/CONTRIBUTING.md

@@ -28,7 +28,7 @@
 
 #### **Running tests and Debugging**
 
-* Expected test output is pulled in as a submodule from the [ImageSharp.Tests.Images repository](https://github.com/SixLabors/Imagesharp.Tests.Images/tree/master/ReferenceOutput). To succesfully run tests, make sure that you have updated the submodules!
+* Expected test output is pulled in as a submodule from the [ImageSharp.Tests.Images repository](https://github.com/SixLabors/Imagesharp.Tests.Images/tree/main/ReferenceOutput). To succesfully run tests, make sure that you have updated the submodules!
 * Debugging (running tests in Debug mode) is only supported on .NET Core 2.1, because of JIT Code Generation bugs like [dotnet/coreclr#16443](https://github.com/dotnet/coreclr/issues/16443) or [dotnet/coreclr#20657](https://github.com/dotnet/coreclr/issues/20657)
 
 #### **Do you have questions about consuming the library or the source code?**

README.md

@@ -1,6 +1,6 @@
 <h1 align="center">
 
-<img src="https://raw.githubusercontent.com/SixLabors/Branding/master/icons/imagesharp.drawing/sixlabors.imagesharp.drawing.512.png" alt="SixLabors.ImageSharp.Drawing" width="256"/>
+<img src="https://raw.githubusercontent.com/SixLabors/Branding/main/icons/imagesharp.drawing/sixlabors.imagesharp.drawing.512.png" alt="SixLabors.ImageSharp.Drawing" width="256"/>
 <br/>
 SixLabors.ImageSharp.Drawing
 </h1>
@@ -37,7 +37,7 @@ Support the efforts of the development of the Six Labors projects.
 ## Documentation
 
 - [Detailed documentation](https://sixlabors.github.io/docs/) for the ImageSharp.Drawing API is available. This includes additional conceptual documentation to help you get started.
-- Our [Samples Repository](https://github.com/SixLabors/Samples/tree/master/ImageSharp) is also available containing buildable code samples demonstrating common activities.
+- Our [Samples Repository](https://github.com/SixLabors/Samples/tree/main/ImageSharp) is also available containing buildable code samples demonstrating common activities.
 
 ## Questions?