This removes the dependency on AppIntro and replaces it with our own custom
intro implementation, backed by ViewPager2. We're doing this because we want a
more reliable and customizable onboarding for Aegis.
I've kept the design mostly the same as it was before, but tried to achieve a
bit of a cleaner look:
<img src="https://alexbakker.me/u/vsr3ahpjt6.png" width="200"> <img
src="https://alexbakker.me/u/efqid2ixly.png" width="200"> <img
src="https://alexbakker.me/u/oehmjm0rn9.png" width="200">
