838410:[Dotnet] ignore include tag when importing comments from xml (#672)

Author: TinaLiu02

.gitignore

@@ -27,3 +27,4 @@ Debug
 /mdoc/mdoc.Test/UwpTestWinRtComponentCpp/x64/Release
 /mdoc.Test.Cplusplus/x64/Release
 /x64/Release/UwpTestWinRtComponentCpp
+/mdoc/Properties/launchSettings.json

mdoc/Mono.Documentation/Updater/DocUtils.cs

@@ -323,7 +323,7 @@ public static bool ClearNodesIfNotDefault(XmlNode n, XmlNode incoming, int depth
                 {
                     if (nchild == null) continue;
 
-                    if (nchild is XmlComment || nchild is XmlText || nchild is XmlCDataSection)
+                    if (nchild is XmlComment || nchild is XmlText || nchild is XmlCDataSection || nchild.Name == "include")
                     {
                         nchild.ParentNode.RemoveChild(nchild);
                         removed = true;