Add example on how to combat clickjacking
Add example on how to combat clickjacking

Give example on how to make Apache provide clickjacking
protection, by sending the `X-Frame-Options` header.

Ref h5bp/server-configs-apache#8.
Close h5bp/server-configs-apache#9.

voku/server-configs-apache,walterebert/server-configs-apache,voku/server-configs-apache,sengkoil/server-configs-apache,h5bp/server-configs-apache,StephanieMak/server-configs-apache,sengkoil/server-configs-apache,atyenoria/server-configs-apache,StephanieMak/server-configs-apache,atyenoria/server-configs-apache,Gillespie59/server-configs-apache,Gillespie59/server-configs-apache,johnnyicarus/server-configs-apache,walterebert/server-configs-apache,blackmoral/server-configs-apache,johnnyicarus/server-configs-apache,blackmoral/server-configs-apache