Add info about luacheck checker for Emacs FLycheck
Add info about luacheck checker for Emacs FLycheck

tst2005/luacheck,xpol/luacheck,mpeterv/luacheck,kidaa/luacheck,linuxmaniac/luacheck,kidaa/luacheck,xpol/luacheck,xpol/luacheck,mpeterv/luacheck,linuxmaniac/luacheck,adan830/luacheck,tst2005/luacheck,mpeterv/luacheck,adan830/luacheck