Add string for pinned system message

app/src/main/res/values-pt-rBR/strings.xml

@@ -55,6 +55,7 @@
     <string name="message_user_joined_channel">Entrou no sala.</string>
     <string name="message_welcome">Bem-vindo, %s</string>
     <string name="message_removed">Mensagem removida</string>
+    <string name="message_pinned">Pinou uma mensagem:</string>
 
     <!-- Message actions -->
     <string name="action_msg_reply">Responder</string>

app/src/main/res/values/strings.xml

@@ -57,6 +57,7 @@
     <string name="message_user_joined_channel">Has joined the channel.</string>
     <string name="message_welcome">Welcome %s</string>
     <string name="message_removed">Message removed</string>
+    <string name="message_pinned">Pinned a message:</string>
 
     <!-- Message actions -->
     <string name="action_msg_reply">Reply</string>