Find a way to showcase no-platform projects

[samtstern]

Right now no-platform projects are only shown via direct linking

[thatfiredev]

Maybe create a new category named "No Platform"?
Then the project.json file would have:

"platforms": [
    "no-platform"
]

Could be a temporary solution until we find a better one. WDYT @samtstern ?

[samtstern]

I think that "No Platform" is pretty confusing, they're all for some platform!

The real issue here is that the home page should probably be something other than a sort-by-platforms list. Even if we added a "No Platform" or "Other" category I doubt anyone would click on it!

[samtstern]

A critical example of something we don't know where to put:
https://github.com/FirebaseExtended/protobuf-rules-gen