add xml comments for uniqueKey

Author: JJ11teen

YamlDotNet/Serialization/BufferedDeserialization/TypeDiscriminators/UniqueKeyTypeDiscriminator.cs

@@ -7,12 +7,24 @@
 
 namespace YamlDotNet.Serialization.BufferedDeserialization.TypeDiscriminators
 {
+    /// <summary>
+    /// A TypeDiscriminator that discriminates which type to deserialize a yaml stream into by checking the existence
+    /// of specific keys.
+    /// </summary>
     public class UniqueKeyTypeDiscriminator : ITypeDiscriminator
     {
         public Type BaseType { get; private set; }
 
         private readonly IDictionary<string, Type> typeMapping;
 
+        /// <summary>
+        /// Initializes a new instance of the <see cref="UniqueKeyTypeDiscriminator"/> class.
+        /// The UniqueKeyTypeDiscriminator will check if any of the keys specified exist, and discriminate the coresponding type.
+        /// </summary>
+        /// <param name="baseType">The base type which all discriminated types will implement. Use object if you're discriminating
+        /// unrelated types. Note the less specific you are with the base type the more yaml will need to be buffered.</param>
+        /// <param name="typeMapping">A mapping dictionary of yaml keys to types.</param>
+        /// <exception cref="ArgumentOutOfRangeException">If any of the target types do not implement the base type.</exception>
         public UniqueKeyTypeDiscriminator(Type baseType, IDictionary<string, Type> typeMapping)
         {
             foreach (var keyValuePair in typeMapping)
@@ -26,6 +38,17 @@ public UniqueKeyTypeDiscriminator(Type baseType, IDictionary<string, Type> typeM
             this.typeMapping = typeMapping;
         }
 
+        /// <summary>
+        /// Checks if the current parser contains of the unique keys this discriminator has in it's type mapping.
+        /// If so, return true, and the matching type.
+        /// Otherwise, return false.
+        /// This will consume the parser, so you will usually need the parser to be a buffer so an instance 
+        /// of the discriminated type can be deserialized later.
+        /// </summary>
+        /// <param name="parser">The IParser to consume and discriminate a type from.</param>
+        /// <param name="suggestedType">The output type discriminated. Null if there target key was not present of if the value
+        /// of the target key was not within the type mapping.</param>
+        /// <returns>Returns true if the discriminator matched the yaml stream.</returns>
         public bool TryDiscriminate(IParser parser, out Type? suggestedType)
         {
             if (parser.TryFindMappingEntry(