chore: add resources found while looking for a local carddev server

knowledge base/carddav.md

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+# CardDAV
+
+Address book protocol extensions for [WebDAV] designed to allow users to access and share contact data on a server in
+the form of [vCard]s.
+
+1. [Further readings](#further-readings)
+
+## Further readings
+
+- [WebDAV]
+- [vCard]
+- [CalDAV]
+
+Implementations:
+
+- [Radicale](https://radicale.org/)
+- [Baikal](https://github.com/sabre-io/Baikal)
+
+<!--
+  Reference
+  ═╬═Time══
+  -->
+
+<!-- In-article sections -->
+<!-- Knowledge base -->
+[caldav]: caldav.md
+[vcard]: vcard.md
+[webdav]: webdav.md
+
+<!-- Files -->
+<!-- Upstream -->
+<!-- Others -->