Allow any branch changes to drainpipe-dev to be pushed to the separate repo

[davereid]

Changes to Consumers

None

Changes to Drainpipe

For any pull request that changes any of the code in the drainpipe-dev directory, it will push the same branch to the drainpipe-dev repository, so that sites can easily test out the changes just with composer and the dev-branch-name requirement syntax.

How to Test

• Review that the latest commit from here is visible on https://github.com/Lullabot/drainpipe-dev/tree/allow-branch-pushes-to-drainpipe-dev
• Review the workflow runs at https://github.com/Lullabot/drainpipe/actions/workflows/DrainpipeDev.yml?query=branch%3Aallow-branch-pushes-to-drainpipe-dev

[justafish]

This has been implemented in https://github.com/Lullabot/drainpipe/blob/main/.github/workflows/DrainpipeDevClean.yml