* Add links to matrix-user-verification-service

Matrix User Authentication Service itself has been available for Jitsi since 42e4e50f5b.

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

* Update README.md

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

* Update docs/container-images.md

* Update roles/custom/matrix-user-verification-service/defaults/main.yml

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Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>
Co-authored-by: Suguru Hirahara <acioustick@noreply.codeberg.org>
Co-authored-by: Slavi Pantaleev <slavi@devture.com>

Signed-off-by: Suguru Hirahara <acioustick@noreply.codeberg.org>

Currently v3.0.0 tested with no issues.
So remove matrix_user_verification_service_docker_image from groups_vars.

/.npm must be writable or an error will be reported.

Related to: https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2375#issuecomment-1655758296

The playbook tries to avoid such variables which are sometimes defined
and sometimes not. We'd rather not check for `is defined`.

Check for empty string instead of Null to verify if an openid_server_name is pinned.

This extends the collection with support for seamless authentication at the Jitsi server using Matrix OpenID.

1. New role for installing the [Matrix User Verification Service](https://github.com/matrix-org/matrix-user-verification-service)
2. Changes to Jitsi role: Installing Jitsi Prosody Mods and configuring Jitsi Auth
3. Changes to Jitsi and nginx-proxy roles: Serving .well-known/element/jitsi from jitsi.DOMAIN
4. We updated the Jitsi documentation on authentication and added documentation for the user verification service.