Support for adding environment variables via GitHub action deploy

### What problem are you trying to solve?

I have several projects deployed to several places. Like one API in Deno Deploy and a Frontend app deployed on Vercel. I like to pass my environment variables in my workflow configuration, it's also easier to manage them since it's all on GitHub instead of distributed on Deno Deploy, Vercel, AWS etc.

But Deno Deploy does not support setting envs from CI.

> Note that currently, this is the only way to add an environment variable. Even if you deployed with deployctl or the Github integration, to add environment variables, you must do so from the project page UI.

Also when I have to run other workflows like for running tests, some of the environment variables are a must. I already have to set them in config but since it does not work for deployment, I just have to duplicate and put it in both places.

### Describe the solution you'd like

Deno Deploy should be able to set environment variables defined in CI.

### Describe alternatives you've considered

-

### Documentation, Adoption, Migration Strategy

_No response_