Interactive SICP JS: should make use of folder mode in chapter 4 and 5

[martin-henz]

It would be nice to organize the programs in SICP JS chapter 4 and 5 into folders, using the new folder mode of Source Academy. For that, we'd need to look at the URL encoding: https://github.com/source-academy/sicp/blob/269071fc4605787c8615e5a07431feefc756889d/javascript/processingFunctions/processSnippetJson.js#L216