I'm working on using embedded-hal-compat for transitioning a side-project form e-h 0.2 to 1.0. It uses the i2c mux driver [xca9548a](https://crates.io/crates/xca9548a) which implements blocking `Write`, `Read`, `WriteRead` but no iterator or transaction traits. The current i2c forwarding is implemented only for an implementation of all i2c traits and `WriteIter`, `Transactional`, ... aren't by xca9548a.

I can easily solve the issue for xca9548a by [adding markers and implementing partial forwarding](https://github.com/sirhcel/embedded-hal-compat/commit/7a08849c1d758353c9affe696c54dec1401dfa3c). But this forces to use explicitly selecting the type of forwarding/the actual marker for all i2c implementing more than `Read` and `Write` like
```rust
use embedded_hal_compat::{Forward, ForwardCompat};
use embedded_hal_compat::markers::ForwardWriteReadWritereadI2c;

```