feat: Add support for keycloak-js@26

[tomaThomas]

PR Checklist

Please check if your PR fulfills the following requirements:

• [x] The commit message follows our guidelines
• [ ] Tests for the changes have been added (for bug fixes / features)
• [x] Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[ ] Bugfix
[x] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

Fixes #583

Does this PR introduce a breaking change?

[ ] Yes
[x] No

Other information

Support for UMD distribution was removed from keycloak-js, which makes it necessary to update the moduleResolution