Fixes based on PR reviews

Author: darrelmiller

src/Microsoft.OpenApi.Readers/OpenApiStreamReader.cs

@@ -21,7 +21,7 @@ public class OpenApiStreamReader : IOpenApiReader<Stream, OpenApiDiagnostic>
         private OpenApiReaderSettings _settings;
 
         /// <summary>
-        /// 
+        /// Create stream reader with custom settings if desired.
         /// </summary>
         /// <param name="settings"></param>
         public OpenApiStreamReader(OpenApiReaderSettings settings = null)

src/Microsoft.OpenApi/Any/OpenApiObject.cs

@@ -17,7 +17,7 @@ public class OpenApiObject : Dictionary<string, IOpenApiAny>, IOpenApiAny
         public AnyType AnyType { get; } = AnyType.Object;
 
         /// <summary>
-        /// 
+        /// Serialize OpenApiObject to writer
         /// </summary>
         /// <param name="writer"></param>
         public void Write(IOpenApiWriter writer)

src/Microsoft.OpenApi/Validations/OpenApiValidator.cs

@@ -15,8 +15,8 @@ namespace Microsoft.OpenApi.Validations
     /// </summary>
     public class OpenApiValidator : OpenApiVisitorBase, IValidationContext 
     {
-
-        private ValidationRuleSet _ruleSet;
+        private readonly ValidationRuleSet _ruleSet;
+        private readonly IList<ValidationError> _errors = new List<ValidationError>();
 
         /// <summary>
         /// Create a vistor that will validate an OpenAPIDocument
@@ -26,9 +26,6 @@ public OpenApiValidator(ValidationRuleSet ruleSet = null)
         {
             _ruleSet = ruleSet ?? ValidationRuleSet.DefaultRuleSet;
         }
-
-        private readonly IList<ValidationError> _errors = new List<ValidationError>();
-
 
         /// <summary>
         /// Gets the validation errors.