Docs: shouldn't remove other attributes from img tags

resolved https://github.com/abpframework/abp/issues/5565

modules/docs/src/Volo.Docs.Web/HtmlConverting/HtmlNormalizer.cs

@@ -49,7 +49,7 @@ namespace Volo.Docs.HtmlConverting
                     var imgTag = match.Groups[0].Value;
                     var title = GetTitleFromTag(imgTag);
 
-                    return $"<a target = \"_blank\" rel=\"noopener noreferrer\" title=\"{title}\" href=\"{link}\"><img src=\"{link}\" alt=\"{title}\"></a>";
+                    return $"<a target = \"_blank\" rel=\"noopener noreferrer\" title=\"{title}\" href=\"{link}\">{imgTag}</a>";
                 });
 
             }
@@ -82,4 +82,4 @@ namespace Volo.Docs.HtmlConverting
             return null;
         }
     }
-}
+}