When specifiying FIRST_USER_NAME, it is not added to sudoers correctly

[FrancisTurner]

If you specify FIRST_USER_NAME in the config file then almost everything works but when
doing sudo with it, you need to enter the password. This is because the file 010_pi-nopasswd in sudoers.d still references user pi and is not changed to FIRST_USER_NAME

The fix is to add the following to stage2/01-sys-tweaks/01-run.sh around line 47

# Add line to replace the username for pi in sudoers.d/010_pi-nopasswd
on_chroot <<EOF
sed "s/pi/$FIRST_USER_NAME/" -i /etc/sudoers.d/010_pi-nopasswd
EOF
# End replace username