The fold() method assumes that the collection is not empty, and starts
with the first element in the collection. A new exception has been added
to handle folds on empty collections. The existing fold() startingWith()
implementation is now more consistent with the new fold() methods.

The readme file is now formatted in the same way as the license file,
and the copyright has been updated to include the current year.

The package file now relies on the newest ESLint, and the lint
configuration has a small update to ensure compatibility with the new
version. A minor issue the linter addressed in the interpreter has also
been fixed.