Fix : warnings on missing documentation

src/.editorconfig

@@ -0,0 +1,4 @@
+[*.cs]
+
+# CS1591: Missing XML comment for publicly visible type or member
+dotnet_diagnostic.CS1591.severity = suggestion

src/Gnu.Getopt/Gnu.Getopt.csproj

@@ -9,5 +9,8 @@
     <SignAssembly Condition=" '$(OS)' != 'Windows_NT' ">false</SignAssembly>
     <AssemblyOriginatorKeyFile>System.Net.IPNetwork.snk</AssemblyOriginatorKeyFile>
   </PropertyGroup>
+  <ItemGroup>
+    <None Include="..\.editorconfig" Link=".editorconfig" />
+  </ItemGroup>
 
 </Project>

src/System.Net.IPNetwork/CidrClassFull.cs

@@ -3,6 +3,9 @@
 
 namespace System.Net
 {
+    /// <summary>
+    /// Class <c>CidrClassFull</c> tries to guess CIDR in a ClassFull way.
+    /// </summary>
     public sealed class CidrClassFull : ICidrGuess
     {
         /// <summary>

src/System.Net.IPNetwork/CidrClassLess.cs

@@ -2,7 +2,9 @@
 
 namespace System.Net
 {
-
+    /// <summary>
+    /// Try to guess a CIDR in a ClassLess way ie. ipv4 = 32, ipv6 = 128
+    /// </summary>
     public sealed class CidrClassLess : ICidrGuess
     {
         /// <summary>

src/System.Net.IPNetwork/CidrGuess.cs

@@ -1,12 +1,30 @@
 namespace System.Net
 {
+     /// <summary>
+     /// 
+     /// </summary>
     public interface ICidrGuess {
+        /// <summary>
+        /// 
+        /// </summary>
+        /// <param name="ip"></param>
+        /// <param name="cidr"></param>
+        /// <returns></returns>
         bool TryGuessCidr(string ip, out byte cidr);
 
     }
+    /// <summary>
+    /// 
+    /// </summary>
     public static class CidrGuess
     {
+        /// <summary>
+        /// 
+        /// </summary>
         public static ICidrGuess ClassFull { get => _cidr_classfull.Value; }
+        /// <summary>
+        /// 
+        /// </summary>
         public static ICidrGuess ClassLess { get => _cidr_classless.Value; }
 
         private static readonly Lazy<ICidrGuess> _cidr_classless = new Lazy<ICidrGuess>(() => new CidrClassLess());

src/System.Net.IPNetwork/IPAddressCollection.cs

@@ -4,13 +4,15 @@
 
 namespace System.Net
 {
-
     public enum FilterEnum
     {
         All,
         Usable
     }
 
+    /// <summary>
+    /// 
+    /// </summary>
     public class IPAddressCollection : IEnumerable<IPAddress>, IEnumerator<IPAddress> {
 
         private readonly IPNetwork _ipnetwork;
@@ -82,12 +84,16 @@ public bool MoveNext()
             }
             return true;
         }
-
+        /// <summary>
+        /// 
+        /// </summary>
         public void Reset()
         {
             _enumerator = -1;
         }
-
+        /// <summary>
+        /// 
+        /// </summary>
         public void Dispose()
         {
             // nothing to dispose