Release v0.3.0

Mostly housekeeping and fixes for this release.

• feat(tracer): adds support for isNoop check on spans. (#181)
• fix(propagation/b3): fix incorrect parsing of a single b3 header (#190)
• chore(examples): makes examples use its own go.mod (#191)
• bump(reporter/amqp): move to migrated and official library github.com/rabbitmq/amqp091-go (#199)
• qa: license date updates, linter fixes, test fixes (#203, #204)
• updated dependencies and regenerated protobuf files (#208)

Thanks all that participated including but not limited to @jcchavezs, @nosan, and @SteelPhase.