chore: update pkg.pr.new workflow

[ota-meshi]

This PR changes the workflow of pkg.pr.new.

The workflow of #1054 is failing with 403 error.
I expect that by splitting the workflow in this PR based on the svelte repository, we can avoid the 403 error.

[changeset-bot]

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[ota-meshi]

Hmm... It seems the new workflow isn't being called.

[ota-meshi]

It seems that the workflow by workflow_run will not work unless we merge this.
I'll try merging this.