Release setup

[aliok]

Changes

• Release tooling and actions
• We have the Backstage plugin and the backend it talks to in the same repo.
• Currently there's only 1 plugin and 1 backend, but we can have multiple in the future in the same repository.
• Golang release will need a trigger (in https://github.com/knative/infra/pull/295 --> to be updated)
• NPM release will be triggered when the Golang trigger creates a release on GitHub (see https://github.com/knative-extensions/backstage-plugins/pull/13/files#diff-f94d9b46e48dd84224634aa7ef4b8f7caae2afa59f5c2f79517da7e7da5fe32bR7-R8).
• NPM release process will get the release version from GitHub release name and publish the NPM package with the same version (see https://github.com/knative-extensions/backstage-plugins/pull/13/files#diff-f94d9b46e48dd84224634aa7ef4b8f7caae2afa59f5c2f79517da7e7da5fe32bR60-R65).
• Until GitHub gives us the NPM knative org (see my message on Slack for the name dispute I've filed), the NPM package is published to knative-extensions NPM org that I own.

/kind

Fixes #

Release Note

Docs

[knative-prow[bot]]

@aliok: The label(s) kind/<kind> cannot be applied, because the repository doesn't have them.

In response to [this](https://github.com/knative-extensions/backstage-plugins/pull/13): > > > > ># Changes > > > >- Release tooling and actions >- Golang release will need a trigger (in https://github.com/knative/infra/pull/295 --> to be updated) >- NPM release will be triggered when the Golang trigger creates a release on GitHub. >- Version bump for NPM release is not done yet. > > >/kind > > >Fixes # > > > >**Release Note** > > >```release-note > >``` > >**Docs** > > >```docs > >``` > Instructions for interacting with me using PR comments are available [here](https://git.k8s.io/community/contributors/guide/pull-requests.md). If you have questions or suggestions related to my behavior, please file an issue against the [kubernetes/test-infra](https://github.com/kubernetes/test-infra/issues/new?title=Prow%20issue:) repository.

[aliok]

cc @knative-extensions/productivity-leads @cardil @upodroid

[aliok]

cc @pierDipi

[knative-prow[bot]]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: aliok, pierDipi

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