Trigger cargo-dist on pushes/merges to default branch

When using GitHub Actions, is there a way to configure `cargo-dist` to run in something similar to `pr-run-mode = "upload"` (where artifacts are uploaded to a workflow run but not added to a release) whenever a PR is merged to `main`/`master` and/or a commit is pushed to that branch, without the user having to also push a tag whenever this happens? Would manually editing `release.yml` to add `on: {push: {branches: [main]}}` be sufficient to get this behavior, or would that just create a mess? If there is currently no way to get this behavior, could you consider supporting it?

Start by reading the generated release.yml workflow and the existing pr-run-mode = "upload" behavior. Check how workflow triggers, default-branch pushes, tags, artifacts, and releases are currently handled. Done means the requested default-branch event behavior is clearly supported or its limitations are documented without creating unintended releases.

Written by the indexing model from the issue text.