Add support for multiple loss functions

[Chronocook]

No description provided.

[Chronocook]

I think it is just set to MAE right now, this should be more explicit as it's super important to learn

[SharathGa]

@Chronocook I am interested to work on this . I am planning to add the following initally-

• Binary cross entropy :- Binary classification.
• categorical cross entropy loss :- Multiclass classification.

[SharathGa]

@Chronocook
#3 As part of Hacktober,

From line 186 to line 230 we have to fix the error.

Creating a class for the loss functions with parameter (target, prediction) :
including the mae, rmse, binary cross entropy and categorical cross entropy.