Fix some typos and add an aka.ms link to regional

Author: bgavrilMS

src/client/Microsoft.Identity.Client/AppConfig/ConfidentialClientApplicationBuilder.cs

@@ -238,8 +238,8 @@ internal override void Validate()
                 throw new MsalClientException(
                     MsalError.RegionalAuthorityValidation,
                     "You configured both Regional Authority and Authority Validation. Authority validation is not currently supported for regional Azure authorities." +
-                    "You can set the validateAuthority flag to false to use Azure Regional authority. Do not disable authority validation if you read the authority from a potentially unstrusted source, " +
-                    "for example from the WWWAuthenticate header of an HTTP request that resulted in a 401 response." );                    
+                    "You can set the validateAuthority flag to false to use Azure Regional authority. Do not disable authority validation if you read the authority from an untrusted source, " +
+                    "for example from the WWWAuthenticate header of an HTTP request that resulted in a 401 response. See https://aka.ms/msal-net-regional for details.");                    
             }
         }
 

src/client/Microsoft.Identity.Client/MsalError.cs

@@ -954,10 +954,10 @@ public static class MsalError
 
         /// <summary>
         /// <para>What happens?</para>You configured both Regional Authority and Authority Validation. Authority validation is not currently supported for regional authorities.
-        /// <para>Mitigation</para>Set the validateAuthority flag to false to use Azure Regional authority. Do not disable authority validation if you read the authority from a potentially unstrusted source, 
+        /// <para>Mitigation</para>Set the validateAuthority flag to false to use Azure Regional authority. Do not disable authority validation if you read the authority from an untrusted source, 
         /// for example from the WWWAuthenticate header of an HTTP request that resulted in a 401 response. 
         ///  </summary>
-        public const string RegionalAuthorityValidation = "regional_autority_validation";
+        public const string RegionalAuthorityValidation = "regional_authority_validation";
 
     }
 }