Adding SetSpellPower for Player

[iThorgrim]

Hello,
In this pull request we are introducing the SetSpellPower method for Player in the Eluna module.

Here's a brief overview of the function:

/**
 * The [Player] sets the spell power
 *
 * @param int value : The spell power value to set
 * @param bool apply = false : Whether the spell power should be applied or removed
 */
int SetSpellPower(lua_State* L, Player* player)
{
    // Function implementation...
}

This allows you to set the spell power of a [Player], indicating the spell power value to set and whether the spell power should be applied or removed.

Tests were carried out over several months on my own server.

Your feedback on this addition would be greatly appreciated.
Kind Regards,

Vaiocti (iThorgrim)