read versionnumber directly from env

we could use `process.env.npm_package_version` instead of reading the version-number with the config-serivce and the env-variables like [here](https://github.com/EddieHubCommunity/api/blob/9813ac19d735da63fa93ceb36e0ffa74b3a76031/src/app.service.ts#L10).
