chore(ios): Move browser out of Keyman app

The built in browser should be moved out of the primary Keyman app for iOS and Android:

1. It is intended for a small subset of languages which do not have good OS-level support for the script.
2. It reduces the complexity of the apps and allows us to improve the usability of the browser app by removing unnecessary app-level navigation.
3. It allows us to label the primary Keyman app as safe for children because the user cannot visit arbitrary web sites.