Add XML comments to public entities.

Interfaces/IFilter.cs

@@ -41,6 +41,10 @@ using System.IO;
 
 namespace Aaru.CommonTypes.Interfaces
 {
+    /// <summary>
+    /// Defines a filter, that is, a transformation of the data from a file, like, for example, a compressor (e.g. GZIP),
+    /// or a container (e.g. AppleDouble)
+    /// </summary>
     public interface IFilter
     {
         /// <summary>Descriptive name of the plugin</summary>