Implement battery percentage detection for laptop users,

[Samdasti]

Add this new function - Cosmos.System.Power.GetBatteryPercentage(); - Returns the value of how many percent the battery is, this function only works for laptop users, if the user is running a desktop, it does nothing, this function can be used in an if statement to do something if the battery percentage is of a certain level, for example:
"if (Cosmos.System.Power.GetBatteryPercentage(); == 0) {
Console.WriteLine("Battery has run out, shutting down...");
System.Threading.Thread.Sleep(1);
Cosmos.System.Power.Shutdown();
}
".

[9xbt]

Duplicate of #2503