[docs] Integrate theme with stackblitz export

The website has a "open in stackblitz" button which works well but is not integrated with the theme system.

Requirements:

1. When I click "open in stackblitz" then the new tab opens in the same theme I had selected on recharts website (dark | light | auto)
2. When I update stackblitz theme on their website using the theme switcher, the Recharts theme also updates