Changed README.md
Changed README.md

Just a small update to the "First boot" section, added a link to "Installer customization" to clarify that the root password can be set during install as well
FooDeas/raspberrypi-ua-netinst,cybercircuits/raspbian-ua-netinst,kolargol/raspbian-ua-netinst,beylsp/rpi-installer,jturner314/raspbian-ua-netinst,matt2005/raspbian-ua-netinst,beylsp/rpi-installer,dicer/raspbian-ua-netinst,yodaaut/raspbian-ua-netinst,Zeerix/raspbian-ua-netinst,bbinet/raspbian-ua-netinst,racing-tech/rrp-raspi-installer,racing-tech/rrp-raspi-installer,malsony/raspbian-ua-netinst,daytonpid/FireHawk,firepick/FireHawk