add dispatched bool output

[aaronsteers]

Resolves #371

• Ability for subsequent step(s) to detect if dispatch was run #371

[peter-evans]

Hi @aaronsteers

Thank you for contributing!

I'm quite happy to add this feature, but please could you make the change in src/main.ts. The dist/index.js file is generated by running npm run build. See here.