add missing CBOR xmldocs (#43882)

src/libraries/System.Formats.Cbor/src/System/Formats/Cbor/CborContentException.cs

@@ -5,21 +5,39 @@
 
 namespace System.Formats.Cbor
 {
+    /// <summary>
+    ///   The exception that is thrown when a CBOR encoding is invalid.
+    /// </summary>
     [Serializable]
     public class CborContentException : Exception
     {
+        /// <summary>
+        ///  Initializes a new instance of the <see cref="System.Formats.Cbor.CborContentException" /> class, using the provided message.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
         public CborContentException(string? message)
             : base(message ?? SR.CborContentException_DefaultMessage)
         {
 
         }
 
+        /// <summary>
+        ///  Initializes a new instance of the <see cref="System.Formats.Cbor.CborContentException" /> class,
+        ///  using the provided message and exception that is the cause of this exception.
+        /// </summary>
+        /// <param name="message">The error message that explains the reason for the exception.</param>
+        /// <param name="inner">The exception that is the cause of the current exception.</param>
         public CborContentException(string? message, Exception? inner)
             : base(message ?? SR.CborContentException_DefaultMessage, inner)
         {
 
         }
 
+        /// <summary>
+        ///   Initializes a new instance of the <see cref="System.Formats.Cbor.CborContentException" /> class with serialized data.
+        /// </summary>
+        /// <param name="info">The object that holds the serialized object data.</param>
+        /// <param name="context">The contextual information about the source or destination.</param>
         protected CborContentException(SerializationInfo info, StreamingContext context)
             : base(info, context)
         {