Item Eco among other fixes

Add items-based economy feature

• Implemented core functionality for items-based economy.
• Updated gradle-wrapper.properties to use Gradle 8.1.1.
• Added configuration loading and saving in PwingEco.java.
• Added a new ReloadCommand class to handle the reload command.
• Updated plugin.yml to include the new pwingeco command and its permission.
• Improved command registration in PwingEco.java.
• Adds Next Tier conversion and whatnot