I think it would be useful to add this package to Expo as it permits to get in app extra data not yet provided by Expo
For example I would like to get in my JS the app version, and the versionCode / buildNumber.
For sure it's possible to rely currently on manifest data, but there's actually no strict guarantee, as far as I know, to ensure that versions in manifest do match version of plist/build.gradle.
For example, one can build a native 1.0.0 app, and yet publish a js bundle with manifest version 2.0.0 which would still install on native 1.0.0 app. By using Expo.Constants.manifest.version, you may actually not get the true native app version but instead the version of the manifest during last JS publish.
This is even more true for detached projects where, as far as I understand, the manifest version-related attributes are not really used anymore.