Fix heading line spacing and padding

[thansidwell]

1. All headings (Heading-2XL, Heading-3XL, etc) have a line height that is too high.
   
   
   Reduce it to about 1.2, so it looks like this.
   
   

2. On page headings the space between the H1, H2 and body are all the same.
   
   Reduce the space between the H1 and H2 to 0 and the space between the h2 and body to 3rem.
   
   Apply to all pages.