Add help doc for "tasks" action

[kitplummer]

tdi 0.0.1
Simple CLI for Microsoft's To Do tasks

USAGE:
    tdi.exe [SUBCOMMAND]

OPTIONS:
    -h, --help       Print help information
    -V, --version    Print version information

SUBCOMMANDS:
    add         Create a new task in ToDo
    complete    Complete the given task
    delete      Delete the given task
    help        Print this message or the help of the given subcommand(s)
    intr        Repl todo shell
    lists       Show the lists in the user's ToDo
    login       Login to Microsoft's Graph database
    logout      Logout of Microsoft's SSO
    me          Show user details
    reopen      Reopen the given task
    show        Display the kanban board
    tasks