OpenResty snippets for Atom

I could not update or unpublish the original repo atom-autocomplete-openresty, so I created the new one here, so bad :)

Updated to OpenResty v1.9.15.1

• lua_ngx
• lua_mysql
• lua_cjson
• lua_upstream

TODOs:

• All OpenResty libraries' snippets (Maybe not ^_^)
• Pull requests are welcome.