- Provide a dummy entry for the JoinHandle enum so that when no other features are enabled the type T is used, this will be disabled in any real use case
- Add spawn_local support directly on the main executor under a feature flag for the executors that can support it (async_std [also with tokio support], wasm, futures ST, tokio ST)
    - spawn_local with multiple executors enable might panic at runtime if used on an unsupported executor
    - Libraries can require the spawn_local feature and be agnostic over a smaller set of executors
    - Support spawn_local in smol using the ideas from async_global_executor
- Add a global block_on function that can be used to inter-operate with sync code
- Support other executors and variants
    - Support async_global_executor (including spawn_local)
    - Support tokio single threaded with spawn_local support
    - Support futures single threaded with spawn_local support
    - Support async_std/smol/... with tokio support (including spawn_local)
- Implement Stream for Interval (under a feature until is in std: https://github.com/rust-lang/rust/issues/79024)
- Get our own macros for main, test, benchmark, ... or recommend using the upstream ones
- Test helpers for specific runtime tests test_in_X other than wasm, also for the native_spawn_local subset to be able to test it (extract common code)
- Write documentation
- Write example crates
- Integrate global tests into common tests so that they can run in wasm
- Use this idea, and maybe make all tests async, to unify all the tests, wasm and native: https://github.com/wasm-rs/async-executor/blob/df48775b37bf62fbc1036a856151b526a3f700ab/src/single_threaded.rs#L288 
- Write more tests