v3.1.0

This release adds:

• seriesmeta: Support for updating the Series ID column (for the Series tab in 4.20.14601).
• kepubify: A new --copy option which allows copying a specified file extension as-is (e.g. kepubify --output /path/to/kobo/kepubify --update --copy .pdf /path/to/books/).

In addition, an issue with kepubify where too many error messages may be shown if 1 or more errors have occurred has been fixed.