Add step to verify the correct Windows Execution Policy for `pnpm setup`

[ProchaLu]

https://upleveled.slack.com/archives/C011BL6759D/p1725553905487039

A student had an issue with the Windows Execution Policy when setting up pnpm with Corepack. We should add a check after running pnpm setup that everything worked and to repeat the step if not

Could be similar to these pnpm verification steps added in #91 :