Enhanced Shopping List Display by Adding Treeview Columns

[prathamesh901]

Overview: This pull request introduces an improvement to the shopping list application by replacing the Listbox with a Treeview widget. The Treeview provides a more structured way to display the shopping list, showing each item and its corresponding amount in separate columns.

Changes Made:

Previously, the shopping list was displayed using a Listbox, where the item and amount were concatenated into a single string and displayed on a single line.
Now, I have replaced the Listbox with a Treeview widget from ttk that supports multiple columns, making it easier to manage and display the shopping list.
The Treeview has two columns:
Item: Displays the name of the item.
Amount: Displays the quantity of the item.

Updated the display_list function:
The display_list function was updated to clear the Treeview widget before inserting the latest items from the shopping_list dictionary.
Each item and its corresponding amount are now displayed in separate columns.

Enhanced UI Layout:
The layout has been adjusted to accommodate the Treeview widget. This enhances the readability of the shopping list by aligning the items and amounts in a structured manner.
I added headers for the columns ("Item" and "Amount") to make it clear what each value represents.

Maintained Existing Functionality:
The core functionalities for adding, removing, and calculating the total items in the shopping list remain unchanged.
Users can still add items with a quantity, remove items, and calculate the total number of items in the list, with the only change being the enhanced visual representation.

Why this change?

• The previous implementation using a Listbox made it difficult to clearly separate and manage items and amounts.
• With this change, the shopping list display is more structured, making it easier for users to view and manage their shopping list items.
• The use of Treeview also opens up possibilities for future enhancements, such as sorting or filtering the shopping list.