✨ Support latest as the default option for the version input

[purpleclay]

What are you trying to do?

I want to stay in sync with the latest version of Dagger while using the GitHub action. However, I have to explicitly set the version to '', which isn't a great developer experience. The version input should default to latest and reflect this in the script and documentation.

Many other GitHub actions use this approach.

Why is this important to you?

Keeping in sync requires manual updates of my GitHub workflows or setting the version to ''. If I am to be explicit, I would prefer to put the version as latest within my workflows.

How are you currently working around this?

I have to manually update my workflows with the version of Dagger that I want.