tweak instructions for non-composer installations
tweak instructions for non-composer installations

IvoPereira/dompdf,edge-soft/dompdf,scotteh/dompdf,scotteh/dompdf,dompdf/dompdf,IvoPereira/dompdf,nathanntg/dompdf,BrunoDeBarros/dompdf,nathanntg/dompdf,BrunoDeBarros/dompdf,edge-soft/dompdf,dompdf/dompdf,IvoPereira/dompdf