Add composing notification

Change-Id: I2c052c4395a56ba6acf882cea3be4b82e2fde761
diff --git a/common/src/interfaces/websocket-interfaces.ts b/common/src/interfaces/websocket-interfaces.ts
index 109adce..f680e16 100644
--- a/common/src/interfaces/websocket-interfaces.ts
+++ b/common/src/interfaces/websocket-interfaces.ts
@@ -30,6 +30,12 @@
   conversationId: string;
 }
 
+export interface ComposingStatus {
+  contactId?: string; // optional (ignored) when is about the user sending it
+  conversationId: string;
+  isWriting: boolean;
+}
+
 export interface CallAction extends ContactMessage {
   conversationId: string;
 }