Foundations Data Types and Conditionals lesson: Clarify replit usage

[ghost]

Because

The Replit instructions implied that the learners needed to click the "Fork" or "Remix" buttons right after creating their Replit account. This PR lets readers know that they need to do that after they have opened the link for the exercises. I also took the liberty of adding a link to Replit since there was none.

This PR

• Adds a link to the Replit website.
• Clarifies the moment in which the learners are expected to fork or remix the exercises in the assignment.

Issue

Closes #28750

Additional Information

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