Release v0.3.0 - Added staged deployment and preview support

[akclace]

Changelog

Added support for staged deployments, see https://clace.io/docs/applications/lifecycle/#staging-apps.
Added support for preview app creation, see https://clace.io/docs/applications/lifecycle/#preview-apps.
Added support for brotli compression for app files in database.
Added HTTP early hints support.

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This discussion was created from the release Release v0.3.0 - Added staged deployment and preview support.