feat: New workflow to remove internal deps from dependabot created prs

[pan-kot]

The new actions workflow is meant to help with Dependabot PRs that usually include internal @cloudscape-design deps that are to be filtered out.

To call the workflow, we need to add this small workflow to all repositories:

name: Dependabot lockfile cleanup

on:
  pull_request:
    types: [opened]

jobs:
  cleanup:
    uses: cloudscape-design/actions/.github/workflows/dependabot-lockfile-cleanup.yml@main

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