1.`v2.1.0` works on Rust Stable from 1.75 (**recommended**), while older versions require a `nightly` compiler via the use of [`#![type_alias_impl_trait]`](https://github.com/rust-lang/rust/issues/63063).
1. Instead of `spawn_after` and `spawn_at`, you now use the `async` functions `delay`, `delay_until` (and related) with impls provided by `rtic-monotonics`.
2. Software tasks _must_ be `async fn`s now. Not returning from a task is allowed so long as there is an `await` in the task. You can still `lock` shared resources.
3. Use `rtic_sync::arbiter::Arbiter` to `await` access to a shared resource, and `rtic_sync::channel::Channel` to communicate between tasks instead of `spawn`-ing new ones.