Add a example of message in integration page

packages/rocketchat-integrations/client/stylesheets/integrations.less

@@ -40,3 +40,9 @@
 		border-bottom: none;
 	}
 }
+
+.message-example {
+	li {
+		list-style: none;
+	}
+}

packages/rocketchat-integrations/client/views/integrationsIncoming.coffee

@@ -15,6 +15,24 @@ Template.integrationsIncoming.helpers
 		return {} =
 			username: 'rocket.cat'
 
+	example: ->
+		return {} =
+			_id: Random.id()
+			msg: 'Example message'
+			bot:
+				i: Random.id()
+			attachments: [{
+				title: "Rocket.Chat"
+				title_link: "https://rocket.chat"
+				text: "Rocket.Chat, the best open source chat"
+				image_url: "https://rocket.chat/images/mockup.png"
+				color: "#764FA5"
+			}]
+			ts: new Date
+			u:
+				_id: Random.id()
+				username: "rocket.cat"
+
 
 Template.integrationsIncoming.events
 	"click .submit > .delete": ->

packages/rocketchat-integrations/client/views/integrationsIncoming.html

@@ -42,6 +42,9 @@
 								</div>
 							</div>
 						{{/if}}
+						<div class="input-line double-col message-example">
+							{{#nrr nrrargs 'message' example}}{{/nrr}}
+						</div>
 					</div>
 				</div>
 				<div class="submit">