Provide v2

[debuglevel]

GitHub Actions usually provide @v2 which would point to the latest @v2.x.y. Would be nice if hadolint would support this too :)

[prantlf]

Now it'd be v3 :-)

The advantage of the extra v<major> tag is less maintenance for projects which use this action and prefer to apply minor and patch version automatically, because they mean no breaking change. As long as there's no breaking change = no major version bump, they'll be able to retain the same action: hadolint/hadolint-action@v3.

The current tagging v<major>.<minor>.<patch> suits very conservative projects, which want to perform every upgrade of build tools explicitly for the p[rice of a higher maintenance effort.