ToggleRefinement not working with Routing URLs example

[yannickcr]

Describe the bug 🐛

When using the ToggleRefinement widget with the routing enabled (following the Routing URLs
guide in the documentation) then the toggle parameter is passed as a string to the widget instead of a boolean.

We got this warning from React:

Warning: Failed prop type: Invalid prop `currentRefinement` of type `string` supplied to `ToggleRefinement`, expected `boolean`.

And when refreshing the page the checkbox is always checked (since we receive the "false" string which is truthy).

This is because the qs module parses the url parameters as string by default (ljharb/qs#91). You can fix this by using qs.decoder (ljharb/qs#91 (comment)) but this is not very convenient (and not precised in the documentation).

To Reproduce 🔍

Steps to reproduce the behavior:

1. Go to https://codesandbox.io/s/example-react-router-b3u4m
2. Click on 'Free shipping'
3. See warning in console.

Expected behavior 💭

The toggle parameter should be correctly passed to the widget as a boolean.

Environment:

• OS: Linux
• Browser: Chrome
• Version: 75

[samouss]

This is something that we are already doing for a couple of widgets e.g. RefinementList. We can implement the logic inside the getCurrentRefinement function of the ToggleRefinement connector.