GitLab

Add licence header to all typescript files in the src and stories directories

Also:
- change the black colour across the site, and add soft-black colour
- update the Checkbox component to change cursor appearance to pointer
  when mousing over label, and to catalogue classNames props
  that can be passed to the Checkbox.
- update the Button component so that the active state of the PrimaryButton and
   SecondaryButton have a 1px-wide border (to avoid changes in button size
   when toggling between disabled and enabled states of the button)
- add option to prettier config to remove trailing commas from objects