Release v0.4.0 (with new pytorch-lightning based API)

Release of Swyft with pytorch-lightning based API.

What's changed

• Training is handled by pytorch-lightning
• More flexible inference network architectures (enabling training of conditional ratios, ratios of different variables, etc)
• New simulation model based on definition of the full graphical model
• New ZarrStore for parallel simulations
• More efficient handling of coverage tests

See tutorial notebooks for example use-cases.

What's next

• Incorporation of all Swyft v0.3.x functionality (violin plots, etc)

Full Changelog: v0.3.2...v0.4.0