Add deploy options

[jhuizy]

What does this PR do?

Adds a deploy_options input to the github action which is appended to the fly deploy ... command allowing the user of the action to configure anything the fly deploy command supports.

Example Usage

name: Staging App
on:
  pull_request:
    types: [opened, reopened, synchronize, closed]

env:
  FLY_API_TOKEN: ${{ secrets.FLY_API_TOKEN }}
  FLY_REGION: iad
  FLY_ORG: personal

jobs:
  staging_app:
    runs-on: ubuntu-latest

    # Only run one deployment at a time per PR.
    concurrency:
      group: pr-${{ github.event.number }}

    # Create a GitHub deployment environment per staging app so it shows up
    # in the pull request UI.
    environment:
      name: pr-${{ github.event.number }}
      url: ${{ steps.deploy.outputs.url }}

    steps:
      - uses: actions/checkout@v4

      - name: Deploy
        id: deploy
        uses: superfly/[email protected]
        with:
          deploy_options: "--build-arg RELEASE_VERSION=beta-${{ github.even.number }}"

Why?

The main use case I had for this was specifying thebuild-arg option. If preferred, we could add that in? Although I think this will solve more use cases and can help if/when fly adds more options to the deploy command.

More Info

I updated the doc on launch_options to be more specific as well.

Open for any feedback/adjustments