Add info about msfconsole.rc to docs

[h00die]

Summary

The msfconsole.rc file, located in linux in ~/.msf4/msfconsole.rc is a special file that runs any time msfconsole is run. This can be useful to set/run things that you always want (setg verbose true, or use exploit/multi/script/web_delivery or multihandler). However, it isn't mentioned in https://docs.rapid7.com/metasploit/resource-scripts/. I think it should be added!