Stabilizing the blocking version

[chrysn]

There have not been any incompatible changes to the blocking versions since 0.2, while async is still behind a feature gate (probably waiting for AFIT to be stabilized).

Is there anything left to do before a 1.0 version can become stable?

Use case is two-fold: the windowed-infinity crate currently plays whack-a-mole with CBOR crates, which all implement their own writers. If there was one semver version of embedded-io (they're all blocking style), I could nudge them all toward a single write type. Moreover, I find myself needing a "Tee" shaped adapter for it (used to write to one writer while simultaneously hashing the input). Using such an adapter across different versions would be quite a nightmare.