[infra] auto-publish pre-releases

[dcharkes]

No description provided.

[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:ffi	2.1.4	already published at pub.dev
package:ffigen	18.1.0	already published at pub.dev
package:jni	0.14.1	already published at pub.dev
package:jnigen	0.14.2-wip	WIP (no publish necessary)
package:native_assets_builder	0.15.0-wip	WIP (no publish necessary)
package:native_assets_cli	0.15.0-0	ready to publish	native_assets_cli-v0.15.0-0
package:native_toolchain_c	0.12.0-wip	WIP (no publish necessary)
package:objective_c	7.1.0	already published at pub.dev
package:swift2objc	0.0.1-wip	WIP (no publish necessary)
package:swiftgen	0.0.1-wip	WIP (no publish necessary)

Documentation at https://github.com/dart-lang/ecosystem/wiki/Publishing-automation.