Validator rejects output generated by codemetapy

[apirogov]

The validator seems to only accept a single hard-coded @context with codemeta, but codemetapy generates a file with context given as a list:

"@context": [
        "https://doi.org/10.5063/schema/codemeta-2.0",
        "https://w3id.org/software-iodata",
        "https://raw.githubusercontent.com/jantman/repostatus.org/master/badges/latest/ontology.jsonld",
        "https://schema.org",
        "https://w3id.org/software-types"
    ],

This is valid JSON-LD, but this validator rejects it.
I understand that implementing the validation fully respecting arbitrary RDF contexts might be difficult for different reasons. But a possible solution could be:

1. If there is more than one context, check that codemeta context URL is part of the list
2. for unknown fields, if there are other contexts beyond codemeta, make a warning instead of an error (because it might be valid for the other contexts)

[progval]

It's a known limitation that this is a generator and not primarily a validator, so it rejects plenty of valid documents. However, for this particular case, #32 should fix it.