Add PayCommand to support player-to-player payments

This commit introduces the PayCommand class, enabling the functionality for players to send payments to each other. The command requires appropriate permissions and is registered using the plugin's lifecycle manager upon initialization.

src/main/java/net/thenextlvl/economist/command/PayCommand.java

@@ -0,0 +1,20 @@
+package net.thenextlvl.economist.command;
+
+import io.papermc.paper.command.brigadier.Commands;
+import io.papermc.paper.plugin.lifecycle.event.types.LifecycleEvents;
+import lombok.RequiredArgsConstructor;
+import net.thenextlvl.economist.EconomistPlugin;
+
+@RequiredArgsConstructor
+@SuppressWarnings("UnstableApiUsage")
+public class PayCommand {
+    private final EconomistPlugin plugin;
+
+    public void register() {
+        var command = Commands.literal("pay")
+                .requires(stack -> stack.getSender().hasPermission("economist.pay"))
+                .build();
+        plugin.getLifecycleManager().registerEventHandler(LifecycleEvents.COMMANDS.newHandler(event ->
+                event.registrar().register(command, "Pay another player")));
+    }
+}