[Website] Add a third party apps marketplace

[yannis300307]

Problem you'd like to fix

Despite some limitations, Epsilon is becoming a pretty interesting calculator OS to develop on. However, there is no unified platform to share 3rd party apps. There is not a lot of 3rd party apps available but most of them are very qualitative such as KhiCas, PeanutGB or Numcraft. The 3rd party apps development community is partly limited by a lack of visibility.

Describe the solution you'd like

Consider adding a third party apps marketplace to the Numworks website similar to the Python scripts library. I deeply believe that Numworks could develop a much bigger development community with a better apps SDK and a sharing platform.
Numworks could be a modular calculator on which you can install what you need. For example, I don't personally need a spreadsheet app but statisticians will need it. They could simply go the the 3rd party apps market place and search for the appropriate app to install. It could reduce the size of the default OS as most of the apps could be optional (I don't use the Finance app for example). An app authentication system could allow some official and certified apps to run in exam mode (Discussed here in #2325 ).
Installing Epsilon could be like the Ninite website on which you can select the apps you want to install in one package.

Describe alternatives you've considered

I'm aware that converting built-in apps to NWA apps is time expansive and not that simple but simply having a basic third party apps marketplace could already be a good addition to the calculator. However I thing that making the calculator more modular could be an excellent idea.

Additional context

I've made a list of well made 3rd party apps here that could be featured.