Resolve "Add POST request to AddPage UI"

Description

• Added POST request to Add class that will enable user to create new to-do items.

Issue

#58 (closed)

Feature

• Allows user to add new to-do items through the UI, including the item's title, description, priority, start date, and due date.

Tophatting

• Checked via GET request that the data was successfully saved.

Expected current behavior

• POST request should be sent with no errors. The item's data should show up when GETting from address "http://127.0.0.1:8080/lists/1/1".

Changes

• Added request and necessary imports to Add class.

Screenshots

Add any screenshots required

Design Patterns

List any design patterns used to accomplish this task

Deviations

Were there any deviations from the original design or architecture plan. If yes, what were they ?

Additional

• Unit test written
• Meets requirements
• Cross-browser tested
• Added/updated documentation as needed
• Camel case style used

Closes #58 (closed)