Missing version in CHANGELOG.md: Calculating the next version fails if tag contains a name/prefix

[restfulhead]

Describe the bug

I'm using auto in a mono repository and my tags contain the name of each sub-package, e.g. my-sub-package-v1.0.0. When generating the changelog, I pass in the previous tag as follows:

npx auto changelog --from my-sub-package-v1.0.0

This works, but causes the version number in CHANGELOG.md to be missing. (The headline that usually renders as <version> (<date>) only displays the current date.)

To Reproduce

• Create a tag with a prefix such as my-sub-package-v1.0.0
• Generate the changelog: npx auto changelog --from my-sub-package-v1.0.0
• Observe that the version is missing in the generated CHANGELOG.md file

Expected behavior
The headline in the Changelog should contain the next version number.

Additional context

calcNextVersion in Release should pass only the number to inc, not the entire tag name. I'm going to submit a pull request in a moment.