add DlaOptions abstract class

src/UglyToad.PdfPig.DocumentLayoutAnalysis/DlaOptions.cs

@@ -0,0 +1,16 @@
+namespace UglyToad.PdfPig.DocumentLayoutAnalysis
+{
+    /// <summary>
+    /// Abstract class that stores options that configure the operation of methods of the document layout analysis algorithm.
+    /// </summary>
+    public abstract class DlaOptions
+    {
+        /// <summary>
+        /// Gets or sets the maximum number of concurrent tasks enabled.
+        /// <para>A positive property value limits the number of concurrent operations to the set value.
+        /// If it is -1, there is no limit on the number of concurrently running operations.</para>
+        /// <para>Default value is -1.</para>
+        /// </summary>
+        public int MaxDegreeOfParallelism { get; set; } = -1;
+    }
+}