Enable selecting by range

## problem
If you want to select continuous lines, you have to use `handleToggleSelection` many times.
But it is inconvenient and lengthy.

## solution
I allowed peco's user to select lines by range with `peco.ToggleSelectMode`.
Using this `SelectMode`, you can select continuous lines with a few key inputs.
This is something like Vim's visual line mode.

![](https://gist.github.com/k0kubun/3d3d0723bc7454936032/raw/04dc3738bfd09d61815ec40d5d8e926951458ddc/ttt.gif)

When peco is not `SelectMode`, you can use an ordinary way to select lines.