Did more config stuff and added to readme.md

src/main/java/me/fivevl/staff/Config.kt

@@ -4,4 +4,6 @@ import org.bukkit.configuration.file.FileConfiguration
 
 object Config {
     var config: FileConfiguration? = null
+    val mustBePlayer = config?.getString("must-be-player")
+    val noPermission = config?.getString("no-permission")
 }

src/main/java/me/fivevl/staff/commands/StaffModeCommand.kt

@@ -1,5 +1,6 @@
 package me.fivevl.staff.commands
 
+import me.fivevl.staff.Config
 import me.fivevl.staff.Utils
 import org.bukkit.command.Command
 import org.bukkit.command.CommandExecutor
@@ -9,10 +10,14 @@ import org.bukkit.entity.Player
 class StaffModeCommand : CommandExecutor {
     override fun onCommand(sender: CommandSender, command: Command, label: String, args: Array<out String>): Boolean {
         if (sender !is Player) {
-            sender.sendMessage(Utils.hex(Utils.getPlaceholders(null, "&cYou must be a player to use this command!")))
+            sender.sendMessage(Utils.hex(Utils.getPlaceholders(null, Config.mustBePlayer!!)))
+            return true
+        }
+        val p = sender.player!!
+        if (!p.hasPermission("staff.staffmode")) {
+            p.sendMessage(Utils.hex(Utils.getPlaceholders(p, Config.noPermission!!)))
             return true
         }
-        val p = sender.player
         return true
     }
 }

src/main/resources/config.yml

@@ -1 +1,2 @@
-must-be-player: "&cYou must be a player to use this command!"
+must-be-player: "&cYou must be a player to use this command!"
+no-permission: "&cYou don't have permission to use this command!"