update-changelog expects an initial release

[kraenhansen]

Because of the prevVersion pattern in the regular expression match on the contents of the changelog, the action fails when performing the initial release of a package:

ci-actions/update-changelog/src/helpers.ts

Line 5 in 6418e15

const changelogRegex = /^## (?<currentVersion>[^\n]*)[^#]*(?<sections>.*?)\n## (?<prevVersion>[^ ]*)/gms;