action failed: ERROR opening file /github/workspace/package-lock.json (undefined)

[MarkLyck]

I don't have a package-lock.json file.

I use yarn not npm. Why is this required?

[kaangokdemir]

This is required for keep syncing versions at package.json and package-lock.json. But that's a good point since currently bumper.ts always assumes project is an npm project. An isNpm condition needed for bumper.ts

I'm so busy nowadays but feel free to create a PR.