Ensure Button component uses correct spacing as link element

When the `Button` component is rendered as link element (`<a>`) by
passing the `href` or `to` prop it'll now use a reduced line height to
ensure it matches the same layout as if it would have been rendered as
`<button>` element.

GH-112

src/components/atoms/core/Button/styles.js

@@ -273,6 +273,8 @@ const base = css`
   background: none;
   padding: 0.375em 0.75em;
   user-select: none;
+  /* Ensure correct spacing when rendering as link element. */
+  line-height: 1.15;
 
   &:hover:not(:disabled) {
     cursor: pointer;