v3.0.0

This major release updates the codemeta library for use with codemeta v3. It will hence-forth output codemeta v3 data only. Codemeta v2 can still be read as input and will be automatically converted. See https://github.com/codemeta/codemeta/releases/tag/3.0 for the codemeta v3 release notes which illustrates the changes. Some notable ones:

• We now use https://w3id.org/codemeta/3.0 as JSON-LD context, instead of https://doi.org/10.5063/schema/codemeta-2.0
• The RDF namespace has not changed between version and remains https://codemeta.github.io/terms/
• Codemeta 3 introduces a isSourceCodeOf property. We now use this instead of schema:targetProduct to link between source code and applications/services. See also: codemeta/codemeta#271 .