Make properties settable

Author: jtjackson

src/ImageSharp.Drawing/Processing/IPen.cs

@@ -28,11 +28,11 @@ public interface IPen
         /// <summary>
         /// Gets the stroke joint style
         /// </summary>
-        public JointStyle JointStyle { get; }
+        public JointStyle JointStyle { get; set; }
 
         /// <summary>
         /// Gets the endcap style
         /// </summary>
-        public EndCapStyle EndCap { get; }
+        public EndCapStyle EndCap { get; set; }
     }
 }

src/ImageSharp.Drawing/Processing/Pen.cs

@@ -76,9 +76,9 @@ public Pen(IBrush brush, float width)
         public ReadOnlySpan<float> StrokePattern => this.pattern;
 
         /// <inheritdoc/>
-        public JointStyle JointStyle { get; }
+        public JointStyle JointStyle { get; set; }
 
         /// <inheritdoc/>
-        public EndCapStyle EndCap { get; }
+        public EndCapStyle EndCap { get; set; }
     }
 }