Restructure solution a bit

src/Spectre.Console/Overflow.cs

@@ -0,0 +1,24 @@
+namespace Spectre.Console
+{
+    /// <summary>
+    /// Represents text overflow.
+    /// </summary>
+    public enum Overflow
+    {
+        /// <summary>
+        /// Put any excess characters on the next line.
+        /// </summary>
+        Fold = 0,
+
+        /// <summary>
+        /// Truncates the text at the end of the line.
+        /// </summary>
+        Crop = 1,
+
+        /// <summary>
+        /// Truncates the text at the end of the line and
+        /// also inserts an ellipsis character.
+        /// </summary>
+        Ellipsis = 2,
+    }
+}