Fixed typings from footer/header margins

[Mil4n0r]

Checklist
(Check off all the items before submitting)

• Build process is done without errors. All tests pass in the /lib directory.
• Self-reviewed the code before submitting.
• Meets accessibility standards.
• Added/updated documentation to /website as needed.
• Added/updated tests as needed.

Description
Footer and Header were accepting an Object as their margin prop, while it made no sense due to only changing margin-top and margin-bottom respectively.

Additional context
The documentation was already updated to display these types

Closes #1710