Feat/add zulip icon

[haennes]

What does this PR change? What problem does it solve?

add zulip socialIcon

Was the change discussed in an issue or in the Discussions before?

license: https://github.com/simple-icons/simple-icons/blob/develop/LICENSE.md

PR Checklist

• [ ] This change adds/updates translations and I have used the template present here.
• [x] I have enabled maintainer edits for this PR.
• [x] I have verified that the code works as described/as intended.
• [x] This change adds a Social Icon which has a permissive license to use it.
• [x] This change does not include any CDN resources/links.
• [x] This change does not include any unrelated scripts such as bash and python scripts.
• [ ] This change updates the overridden internal templates from HUGO's repository.

[sonarqubecloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[haennes]

Bump :) Any reason not to merge this? Any fixes i should make?