Tag the 0.9.0 release

[flavio]

Prepare 0.9.0 release

This is a minor release since some API have been changed.

== What's Changed

• sign: init by @jleightcap in https://github.com/sigstore/sigstore-rs/pull/310
• cargo audit: ignore RUSTSEC-2023-0071 by @jleightcap in https://github.com/sigstore/sigstore-rs/pull/321
• chore(deps): Update json-syntax requirement from 0.9.6 to 0.10.0 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/319
• chore(deps): Update cached requirement from 0.46.0 to 0.47.0 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/323
• chore(deps): Update serial_test requirement from 2.0.0 to 3.0.0 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/322
• dep: update rustls-webpki, fold in pki_types by @jleightcap in https://github.com/sigstore/sigstore-rs/pull/324
• chore(deps): Update cached requirement from 0.47.0 to 0.48.0 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/325
• chore(deps): Update json-syntax requirement from 0.10.0 to 0.11.1 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/327
• chore(deps): Update cached requirement from 0.48.0 to 0.49.2 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/329
• chore(deps): Update json-syntax requirement from 0.11.1 to 0.12.2 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/330
• lint: fix lint error of chrono and tokio by @Xynnn007 in https://github.com/sigstore/sigstore-rs/pull/334
• chore(deps): Update base64 requirement from 0.21.0 to 0.22.0 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/332
• The Repository trait and ManualRepository struct no longer require a feature flag by @tannaurus in https://github.com/sigstore/sigstore-rs/pull/331
• chore(deps): Bump actions/checkout from 4.1.1 to 4.1.2 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/336
• chore(deps): Update reqwest requirement from 0.11 to 0.12 by @dependabot in https://github.com/sigstore/sigstore-rs/pull/341
• update tough dep by @astoycos in https://github.com/sigstore/sigstore-rs/pull/340

== New Contributors

• @tannaurus made their first contribution in https://github.com/sigstore/sigstore-rs/pull/331
• @astoycos made their first contribution in https://github.com/sigstore/sigstore-rs/pull/340

Full Changelog: https://github.com/sigstore/sigstore-rs/compare/v0.8.0...v0.9.0