codemeta: copyrightYear should be number

[tmorrell]

datatools/codemeta/codemeta.go

Line 47 in d0bf489

CopyrightYear string `json:"copyrightYear,omitempty"`

should be a number, not a string

Example file https://github.com/caltechlibrary/template/blob/main/codemeta.json