Add Tapioca compiler for models with `ejects_to` defined

[maxveldink]

When eject is called on an instance of an ActiveRecord model that defines ejects_to, Sorbet does not know the method exists. Further, we don't know what the return type should be, so we're forced to use the typed: false sigil.

Tapioca allows for custom compilers to generate RBIs for a project based on given conditions. We should add one for ejection_seat to give more type information.