[Feature] Add Experience Gain Toggle. (#2676)

* [Feature] Add Experience Gain Toggle.

# Perl
- Add `$client->IsEXPEnabled()`.
- Add `$client->SetEXPEnabled(is_exp_enabled)`.

# Lua
- Add `client:IsEXPEnabled()`.
- Add `client:SetEXPEnabled(is_exp_enabled)`.

# Commands
- Add `#exptoggle [Toggle] - Toggle your or your target's experience gain.`.

# Notes
- Allows operators to turn on/off a player's experience gain individually without changing their rule values.
- The command allows operators to give players access to the command to disable their own experience gain.

zone/gm_commands/exptoggle.cpp

@@ -0,0 +1,28 @@
+#include "../client.h"
+
+void command_exptoggle(Client *c, const Seperator *sep)
+{
+	auto arguments = sep->argnum;
+	if (!arguments || arguments > 1) {
+		c->Message(Chat::White, "Usage: #exptoggle [Toggle] - Toggle your or your target's experience gain.");
+		return;
+	}
+
+	auto t = c;
+	if (c->GetTarget() && c->GetTarget()->IsClient() && c->GetGM()) {
+		t = c->GetTarget()->CastToClient();
+	}
+
+	const auto is_exp_enabled = Strings::ToBool(sep->arg[1]);
+
+	t->SetEXPEnabled(is_exp_enabled);
+
+	c->Message(
+		Chat::White,
+		fmt::format(
+			"Experience gain for {} is now {}abled.",
+			c->GetTargetDescription(t, TargetDescriptionType::LCSelf),
+			is_exp_enabled ? "en" : "dis"
+		).c_str()
+	);
+}