Remove permission_handler

[ccadieux]

Having permission_handler as part of this library makes it hard to use. We use permission_handler in our app so now if we want to update permission_handler we need to use dependency_overrides to work with this package.

Most libraries just tell you what permissions are required in the Readme and it's the responsibility of the developers to handle that. Using the example app to show that would be better than having this dependency as part of the package.

Looking at closed PRs there are 4 that reference permission_handler issues. Seems like this will continue until you remove the dependency.