Support .denoignore

### What problem are you trying to solve?

I have more than a few files that are needed to be excluded from the deployment. The flag `--exclude` is no longer helpful if I need a short command.

### Describe the solution you'd like

I think an git-like ignore file would be very helpful for project that have trash files scatter everywhere.

### Describe alternatives you've considered

Or we can just use the `deno.json` file with key `deploy.exlude` for this task. It is good as well. Even better, the developers can use multiple Deploy accounts for different projects by using a key (e.g. `deloy.token`) in `deno.json` instead of 1 big env var `DENO_DEPLOY_TOKEN`.

### Documentation, Adoption, Migration Strategy

_No response_

The issue names no repository files, tests, or entry points. Start by clarifying whether support should use a .denoignore file or deno.json configuration alongside --exclude, then define the ignore behavior and confirm that deployments exclude the intended files.

Written by the indexing model from the issue text.