Projects: use next challenge's seed as a solution

Is your feature request related to a problem? Please describe.

The new project based curriculum typically uses the solution to challenge n as the seed for challenge n + 1. As such, there’s a lot of code duplication.

Describe the solution you’d like

The ability to reference another challenge and import it’s seed as a solution. Perhaps using the following template:

## Solution
<section id='solution'>

<div id='challenge-solution' seed-id='id-of-the-next-challenge'>
</div>

</section>

As yet I’ve not put much time into working out how feasible this is, I just noticed @scissorsneedfoodtoo’s comment https://github.com/freeCodeCamp/freeCodeCamp/pull/36873#issuecomment-538846699 and thought it was worth discussing.

Edit: I mixed up the seed and the solution, fixed now.

[ojeytonwilliams]

I’m closing this since, when a solution is missing, challenge n automatically uses challenge n + 1’s seed as it’s solution.

[scissorsneedfoodtoo]

@ojeytonwilliams, using the meta.json file to query the next file for the solution section sounds like a good idea. Even when we start to support multiple files/directories, we’ll still essentially be testing one file at a time.