Add CHANGELOG entry for solid-test (#530,#546).

Author: RubenVerborgh

CHANGELOG.md

@@ -9,6 +9,9 @@
   The Solid server acts as a reverse proxy for these paths, forwarding requests
   to the back-end server along with the authenticated user (`User` header)
   and the host through which Solid is being accessed (`Forwarded` header).
+- Self-signed certificates are no longer trusted in production.
+  To allow self-signed certificates (for testing purposes), use `bin/solid-test`,
+  which sets `NODE_TLS_REJECT_UNAUTHORIZED=0` and `--no-reject-unauthorized`.
 
 #### 4.0.0 Upgrade Notes
 - The `proxy` configuration parameter has been deprecated and