Crane theme supports embeding custom HTML (incliding inline JS) and CSS.

Additional CSS

One field is for CSS and it is placed in Appearance -> Customizer -> Additional CSS (Starting from version 4.7, WordPress implemented it's own field for custom CSS. In future releases we will place this field in Theme options settings nerby Custom HTML field to make it more obviously).

Custom HTML

Another field is for custom HTML code. You can insert metric code in this field and this code will be loaded on all pages of your site. Be sure that you wrap JS code in <script> tag. Otherwise it will be rendered as plain html.