Slug for Category or Tag should be generated automatically

[subrataemfluence]

When adding a Category or Tag in admin, Slug generation should be automated based on category / tag name entered in Name box and Slug box would be populated with it.

Advantages:
(1) user won't have to type in the slug by hand, hence saves time
(2) will minimize the typographic error.

The slug box will remain editable and users still have the ability to change slug if required.

Core file: wp-admin/edit-tags.php
Script added under line 581

[subrataemfluence]

Previous diff was using wrong pattern.