Keycloak JS 26.2.1 released

This release of Keycloak JS is the first release after our initial announcement to split if off from the main project release cycle. This release is the result of a large internal refactor to make the code more maintainable and make use of modern JavaScript language features, as well as to introduce a new test suite with more comprehensive test coverage. Even though much has changed under the hood, this is a patch releases, and there should be no breaking changes for users, only bugfixes and small enhancements.