Ability to define steps within the plugin

I have a number of operations that I would like to execute within the container. There are node tests, linting, type checking, building, python tests and linting and type checking... that's arguably a lot of stuff. Yet, currently everything goes into a single step in GitHub actions - the container build step.

Rather than define everything in the `runCmd` property, I would like to be able to define basic steps as

```
steps:
- name: Run node tests
run: pnpm run test
- name: Linting
run: pnpm run lint
...
```

And that would end up in separate steps within GitHub actions.