dm page : Implement "No DMs yet" UI design

Implemented the UI for the "No DMs yet" state on the RecentDmConversationsPage according to the design provided.

Fixes part of zulip#127

Author: Dhanesh-Sawant

assets/icons/ZulipIcons.ttf

@@ -99,35 +99,41 @@ abstract final class ZulipIcons {
   /// The Zulip custom icon "mute".
   static const IconData mute = IconData(0xf119, fontFamily: "Zulip Icons");
 
+  /// The Zulip custom icon "no_dm".
+  static const IconData no_dm = IconData(0xf11a, fontFamily: "Zulip Icons");
+
+  /// The Zulip custom icon "no_dm_down_arrow".
+  static const IconData no_dm_down_arrow = IconData(0xf11b, fontFamily: "Zulip Icons");
+
   /// The Zulip custom icon "read_receipts".
-  static const IconData read_receipts = IconData(0xf11a, fontFamily: "Zulip Icons");
+  static const IconData read_receipts = IconData(0xf11c, fontFamily: "Zulip Icons");
 
   /// The Zulip custom icon "send".
-  static const IconData send = IconData(0xf11b, fontFamily: "Zulip Icons");
+  static const IconData send = IconData(0xf11d, fontFamily: "Zulip Icons");
 
   /// The Zulip custom icon "share".
-  static const IconData share = IconData(0xf11c, fontFamily: "Zulip Icons");
+  static const IconData share = IconData(0xf11e, fontFamily: "Zulip Icons");
 
   /// The Zulip custom icon "share_ios".
-  static const IconData share_ios = IconData(0xf11d, fontFamily: "Zulip Icons");
+  static const IconData share_ios = IconData(0xf11f, fontFamily: "Zulip Icons");
 
   /// The Zulip custom icon "smile".
-  static const IconData smile = IconData(0xf11e, fontFamily: "Zulip Icons");
+  static const IconData smile = IconData(0xf120, fontFamily: "Zulip Icons");
 
   /// The Zulip custom icon "star".
-  static const IconData star = IconData(0xf11f, fontFamily: "Zulip Icons");
+  static const IconData star = IconData(0xf121, fontFamily: "Zulip Icons");
 
   /// The Zulip custom icon "star_filled".
-  static const IconData star_filled = IconData(0xf120, fontFamily: "Zulip Icons");
+  static const IconData star_filled = IconData(0xf122, fontFamily: "Zulip Icons");
 
   /// The Zulip custom icon "topic".
-  static const IconData topic = IconData(0xf121, fontFamily: "Zulip Icons");
+  static const IconData topic = IconData(0xf123, fontFamily: "Zulip Icons");
 
   /// The Zulip custom icon "unmute".
-  static const IconData unmute = IconData(0xf122, fontFamily: "Zulip Icons");
+  static const IconData unmute = IconData(0xf124, fontFamily: "Zulip Icons");
 
   /// The Zulip custom icon "user".
-  static const IconData user = IconData(0xf123, fontFamily: "Zulip Icons");
+  static const IconData user = IconData(0xf125, fontFamily: "Zulip Icons");
 
   // END GENERATED ICON DATA
 }