Fix overflowing headers on small screens (#1830)

src/theme.js

@@ -89,6 +89,11 @@ const fonts = {
     lineHeight: '65px',
     fontWeight: 700,
 
+    [media.lessThan('small')]: {
+      overflowWrap: 'break-word',
+      wordBreak: 'break-word',
+    },
+
     [media.lessThan('medium')]: {
       fontSize: 40,
       lineHeight: '45px',