Release a tagged version with Tracing 0.3.0 (Sendable)

[Konrad `ktoso` Malawski]

There's a WIP here https://github.com/slashmo/opentelemetry-swift/tree/ci/api-breakage and people are eager to adopt even while the library is pre-1.0 :-)

Let's use this momentum to get feedback no the tracing APIs