Update the typography and font size of the text across the whole Jenkins core UI.
Changes will include: * Normalize the base font size to a base of 14px, using smaller fonts of 12px and 16px when needed. * Use a base line height of 1.5 for body copy * Establishing a basic headings hierarchy * Use system fonts as the default types
On the setup wizard there will only be type updates, no font sizes. This is due to the fact that changing the font sizes would probably cause the layout to break.