Allow Lumi to open, edit and save unzipped H5P packages

[Aratch]

Problem description/rationale
Lumi currently does not support opening and editing unzipped H5P packages. Though somewhat advanced and specific, this feature may be useful in the following ways:

1. Version Control: Although there are ways to make git use external tools to extract and re-compress archive files on each diff (see below), allowing Lumi to open, edit and save unzipped H5P packages in file-and-directory form as-is would make quasi non-destructive editing painless. The contents of H5P packages are plain-text (save for binary data like media), human-readable (if one wishes to do so). Merging two different branches should work flawlessly.
2. (Custom) H5P Development/Editing: I know, there is the H5P CLI toolkit and obviously other ways to go about this, but sometimes you just want to attempt minor changes to packages or libraries. Additionally, some more "advanced" libraries are limited in their usability and functionality in my personal experience, namely the iframe embedder.

A cursory reading of the Lumi source code hasn't yielded any concrete ways to implement this, yet (I have limited node.js experience), so I can't say how much work this is.

Solution
Allow Lumi to open, display, edit and - most importantly - save unzipped H5P packages as-is by identifying (and checking for) h5p.json, content/ and libraries/dependencies.

Alternatives
Feasible but otherwise not functionally equivalent alternatives to the use cases mentioned above:

1. Write a utility like xls2txt and set up git attributes to use that for diffs. This, however, does not allow for merging or any other useful VCS functionality.
2. Unzip and rezip H5P archives: Seems to be error-prone, hard to keep track of changes and introduces several additional manual steps.

Additional context
My personal use case: I'm developing in-house WBT/e-learning content for a mid-size organisation, some of it custom-coded - most, however, is made with a certain software suite by a certain company. Lumi allows for more flexibility and reusability, as well as more engaging activities that need less manual work (also, H5P is being actively developed).