Fixed Badge typing for label

[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
Type shown in the documentation for the label prop inside Badge component was wrong. It can be either string or number based on the mode (string for contextual, number for notification)

Additional context
The typing has been slightly modified for notification mode to use "" in case of not wanting to display content inside, instead of having to work with a possibly undefined value, allowing label to have a default value of "" just like it is done in, for example Button component. Changing the typing of the notification mode in the code was not required