feat: Allow creating of usage guide

[ethanrucinski]

I have been looking for ways to automate producing documentation for GitHub actions and this is an awesome tool to learn about; thanks for building it!

One of my favorite ways to document reusable actions is to create "usage" section which is a chunk of YAML similar to this: https://github.com/actions/checkout#usage

I think this style of guide is visually appealing, but more importantly I also think it helps users who are new to GitHub actions by providing unambiguous syntax for how your action should be used. I have added an optional comment block action-docs-usage which, when provided, will add a usage guide. I used this in my sample project here: https://github.com/ethanrucinski/test-usage-guide

As an aside, I also added the __tests__ directory to the .eslintignore as it is not covered by the .tsconfig.json.

I hope you will consider my pull request and give me any feedback you have on my code!

[npalm]

Cool idea, would be nicer if a more tailed usages example could be provided. But that could be a nice step for the future.

[ethanrucinski]

Cool idea, would be nicer if a more tailed usages example could be provided. But that could be a nice step for the future.

Sure I can add more in the future if you like