feat: add post-quick-reply language key

languages/en-GB/persona.json

@@ -1,3 +1,4 @@
 {
-    "mobile-menu-side": "Switch which side each mobile menu is on"
+    "mobile-menu-side": "Switch which side each mobile menu is on",
+    "post-quick-reply": "Post quick reply"
 }

templates/partials/topic/quickreply.tpl

@@ -14,7 +14,7 @@
 		<div class="quickreply-message">
 			<textarea name="content" component="topic/quickreply/text" class="form-control" rows="5"></textarea>
 		</div>
-		<button type="submit" component="topic/quickreply/button" class="btn btn-primary pull-right">Post quick reply</button>
+		<button type="submit" component="topic/quickreply/button" class="btn btn-primary pull-right">[[persona:post-quick-reply]]</button>
 	</form>
 </div>
 <!-- ENDIF privileges.topics:reply -->