fixes readme typo for italic style setting
fixes readme typo for italic style setting

I was having problems with the italics style setting... the problem was the readme docs for it. The setting should be *italics* no *italic*.
Nishi-Inc/pdfmake,naoa/pdfmake,Intia/pdfmake,naoa/pdfmake,mweslander/pdfmake,jiusanzhou/pdfmake,mdoelker/pdfmake,mdoelker/pdfmake,TW-QEN/pdfmake,atsuyim/pdfmake,mweslander/pdfmake,TW-QEN/pdfmake,compact/pdfmake,atsuyim/pdfmake,wbswbs/pdfmake,Intia/pdfmake,jodeng110/udpcloud-pdfmake,dennisrjohn/pdfmake,compact/pdfmake,Novlr/pdfmake,tanem/pdfmake,mubassirhayat/pdfmake,mubassirhayat/pdfmake,tanem/pdfmake,Nishi-Inc/pdfmake,jodeng110/udpcloud-pdfmake,bavellone/pdfmake,bavellone/pdfmake,jiusanzhou/pdfmake,Novlr/pdfmake,dennisrjohn/pdfmake,wbswbs/pdfmake,pfarnach/pdfmake,pfarnach/pdfmake