Use expo-sharing to allow users to share/download tcx files from the phone #92
Description
Currently expo-filesystem doesn't allow us to write the files to anywhere that the OS filesystem browser can access (see: https://expo.canny.io/feature-requests/p/ability-to-save-files-on-internal-storage). Instead what is suggested is to use the expo-sharing sdk https://docs.expo.dev/versions/latest/sdk/sharing/ . We could enable this from the historical rides page, so a user could select a ride and share it to whatever they want. This would be essential for users that don't want to auto sync to strava.