SmartEnumStringComparer not included in 7.0.0 version

README specifies comparing string values case insensitive [here](https://github.com/ardalis/SmartEnum#case-insensitive-string-enum) but this attribute doesn't exists in package. I'm assuming that publishing to nuget failed [details](https://github.com/ardalis/SmartEnum/actions/runs/5836315104/job/15829639986).

Start by checking the README's case-insensitive string enum example and the contents of the 7.0.0 package. Review the linked GitHub Actions run for the publishing failure and compare the package with the expected SmartEnumStringComparer attribute. Done means the attribute is included in the published package and the documented example works.

Written by the indexing model from the issue text.