docs: document how to open a dark themed checkout #7100
Description
$40
We need a new guide on "Switching themes in the checkout"
section 1. In this we need to show how a checkout session can be created using the API and then appending the theme query param as dark or light would allow to change the theme of the genearted checkout session so that the end user sees it in that mode
section 2. Similarly, we need to show that in checkout links the theme can be adjusted by using the parameter ?theme=dark or light (no need to show an API call here)
having images would be helpful
@shubhi2000 do you want to attempt this ahead of other issues?