BccButton disabled doesn't work in combination with the `:is` component param

[StevenMalaihollo]

Describe the bug

When setting the BccButton to disabled while using the is to enter in the component that the button is supposed to be, the disabled state is not taken into account.

Expected behavior

The styling and functionality of the disabled state should continue working when using the RouterLink component as BccButtons param.

root cause: commit_id

[laurensgroeneveld]

This is because the :disabled modifier is used to set the styles, but the disabled attribute only works on a button not an a element (even though it is set, it doesn't take effect). https://github.com/bcc-code/bcc-design/blob/main/design-library/src/components/BccButton/BccButton.css#L4