[github] Add a manual workflow to publish openai-deno-build

[athyuttamre]

• I understand that this repository is auto-generated and my pull request may not be merged

Changes being requested

Adds a new GitHub workflow that can be run manually to publish the latest tag to the openai-deno-build repo. All pushes to that repo are published to https://deno.land/x/openai.

The publishing to the Deno repo will happen using the credentials of the newly set up "OpenAI Open Source" GitHub App. I've added the secrets APP_ID and APP_PRIVATE_KEY to the publish environment.

I've tested this works by:

• Forking the openai-node and openai-deno-build repos
• Creating my own GitHub App that is installed in both
• Running the workflow, and confirming that the latest tag is pushed from the source repo to the destination repo

If this manual publishing step works correctly, I will update the create-releases.yml workflow to use the same steps to enable auto-publishing. To ensure we don't publish broken tags to https://deno.land/x/openai, I will disable webhooks on the openai-deno-build repo until I'm sure the publishing from openai-node to openai-deno-build works correctly.

Additional context & links

[rattrayalex]

Great!