Trigger cargo-dist on pushes/merges to default branch

[jwodder]

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?