other shell repository

add other webshell collect repository
url : https://github.com/tdifg/WebShell

add public-shell repository
url : https://github.com/BDLeet/public-shell

add web-backdoors
url : https://github.com/all3g/fuzzdb/tree/master/web-backdoors

add web-shell
url : https://github.com/BlackArch/webshells

add webshellSample
url : https://github.com/tanjiti/webshellSample

add Ridter'Pentest backdoor tools
url : https://github.com/Ridter/Pentest/tree/master/backdoor

add xl7dev'WebShell
https://github.com/xl7dev/WebShell  小乐天 From: Knownsec