feat: add PLAYER_EVENT_ON_CAN_SEND_MAIL

[r-o-b-o-t-o]

Adds a new Player event:

PLAYER_EVENT_ON_CAN_SEND_MAIL = 49, // (event, player, receiverGuid, mailbox, subject, body, money, cod, item) - Can return false to prevent sending the mail

Example Lua snippet:

local PLAYER_EVENT_ON_CAN_SEND_MAIL = 49

local function OnSendMail(event, player, receiverGuid, mailbox, subject, body, money, cod, item)
	local receiver = GetPlayerByGUID(receiverGuid)
	if (receiver ~= nil) then
		print(player:GetName() .. " wants to send a mail to " .. receiver:GetName())
	else
		print(player:GetName() .. " wants to send a mail to " .. tostring(receiverGuid))
	end
	print("Subject: " .. subject)
	if money > 0 then
		print("Attached: " .. tostring(money) .. " copper")
	end
	if item ~= nil then
		print("Attached: " .. item:GetName())
	end
	if cod > 0 then
		print("COD: " .. tostring(cod) .. " copper")
	end
	print("Body:")
	print(body)

	return false -- prevent the mail from being sent
end
RegisterPlayerEvent(PLAYER_EVENT_ON_CAN_SEND_MAIL, OnSendMail)