styles.py: add support for h4-h6
styles.py: add support for h4-h6

Distrotech/reportlab,kanarelo/reportlab,kanarelo/reportlab,Distrotech/reportlab,Distrotech/reportlab,kanarelo/reportlab,Distrotech/reportlab,kanarelo/reportlab,kanarelo/reportlab,Distrotech/reportlab