Docs: Add information about the `robots.txt` file
Docs: Add information about the `robots.txt` file

Ref https://github.com/h5bp/html5-boilerplate/pull/1598

xieQin/mobile-boilerplate,h5bp/mobile-boilerplate,globalepub/mobile-boilerplate,xzcb2008/mobile-boilerplate,Saajan/uber-mobile,globalepub/mobile-boilerplate,wjb12/mobile-boilerplate,Saajan/uber-mobile,COBSNAN/mobile-boilerplate,cyprianos/bold,perfect-pixell/mobile-boilerplate,filtercake/mobile-boilerplate-timetable-3,h5bp/mobile-boilerplate,xieQin/mobile-boilerplate,xzcb2008/mobile-boilerplate,COBSNAN/mobile-boilerplate,cyprianos/bold,perfect-pixell/mobile-boilerplate,wjb12/mobile-boilerplate,filtercake/mobile-boilerplate-timetable-3