add importance (#3885)

Author: Tom Laird-McConnell

CSharp/Library/Microsoft.Bot.Connector.Shared/Importance.cs

@@ -0,0 +1,27 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Microsoft.Bot.Connector
+{
+    /// <summary>
+    /// Defines the importance of an Activity
+    /// </summary>
+    public static class ActivityImportance
+    {
+        /// <summary>
+        /// Low importance.
+        /// </summary>
+        public const string Low = "low";
+
+        /// <summary>
+        /// Normal importance.
+        /// </summary>
+        public const string Normal = "normal";
+
+        /// <summary>
+        /// High importance.
+        /// </summary>
+        public const string High = "high";
+    }
+}

CSharp/Library/Microsoft.Bot.Connector.Shared/Microsoft.Bot.Connector.Shared.projitems

@@ -80,6 +80,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)IInstallationUpdateActivity.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)IInvokeActivity.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)IMessageActivity.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)Importance.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)InputHints.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)ITypingActivity.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)JwtConfig.cs" />