Add automatic version from package.json

[angiehjort]

For all our projects including this one we need to be able to know the version easily when using the package
Please add a baked-in version constant

observable:
DDFCsvReader = require('https://unpkg.com/@vizabi/reader-ddfcsv@4.3.3')
DDFCsvReader.version
DDFCsvReader.versionInfo

frontend:
import "@vizabi/reader-ddfcsv/dist/reader-ddfcsv.js";
DDFCsvReader.version
DDFCsvReader.versionInfo

backend:
import DDFCsvReader from "@vizabi/reader-ddfcsv";
DDFCsvReader.version
DDFCsvReader.versionInfo

.version should return a string like "4.3.3"
.versionInfo should return an object like in vizabi core
build is a timestamp in milliseconds

.version and .versionInfo.version is the same thing
it's redundant but more idiot-proof