[3.15] Adding an attribute for the TLS registry reference guide

[MichalMaler]

Adding an attribute for the TLS registry reference guide.
Cherry-pick of c265a8b of #43446

[aloubyansky]

FYI @gsmet

[MichalMaler]

Hello @aloubyansky and @gsmet. I just wanted to have this little thing merged and backported so that I can test it before handing it all over to QE; thus, I opted for the manual cherry-pick backport directly to 3.15 instead of just putting a label on my "main" PR. Hope I didn't created any mess :) In most cases, I will go with the normal flow of just creating PRs against main and adding the label.

Please let me know if this is OK.
I removed the backport label in my original PR: #43446

[github-actions]

🙈 The PR is closed and the preview is expired.

[quarkus-bot]

Status for workflow Quarkus Documentation CI

This is the status report for running Quarkus Documentation CI on commit 7b841c8.

✅ The latest workflow run for the pull request has completed successfully.

It should be safe to merge provided you have a look at the other checks in the summary.

[gsmet]

I have a vague recollection that we had issues with attributes in titles on the website but apparently it works now: https://quarkus.io/version/main/guides/tls-registry-reference .