feat: add GetRank method for creatures

[kabigon143]

Introduces the GetRank method. Rank is used in creature_template to set the rank of the creature, e.g. rare (4) or rare elite (2).

You can test this in game with this lua script:

local command = "#rank"
local function FetchCreatureRank(event, player, message, type, language)
    if message == command then
        local creature = player:GetSelection() -- Get the player's target

        if creature then
            local rank = creature:GetRank() -- Fetch the rank of the selected creature

            if rank then
                print("Creature Rank: " .. rank) -- Print the creature's rank
            else
                print("Creature rank not available.")
            end
        else
            print("No creature selected.")
        end

        return false -- Prevent the default chat behavior
    end
end
RegisterPlayerEvent(18, FetchCreatureRank)

If the player types "#rank" while having targeted a creature, the script will print the creature's rank to the console.

[55Honey]

Thanks for the PR!