Add documentation for new certificate configuration options

Signed-off-by: Lukas Straub <lukasstraub2@web.de>

docs/manual/configuring.rst

@@ -553,3 +553,15 @@ To enable the previous behavior, add to config::
   enable_flash_video_rewrite: true
 
 The system may be revamped in the future and enabled by default, but for now, it is provided "as-is" for compatibility reasons.
+
+Verify SSL-Certificates
+-----------------------
+
+By default, SSL-Certificates of websites are not verified. To enable verification, add the following to the config::
+
+  certificates:
+    cert_reqs: 'CERT_REQUIRED'
+    ca_cert_dir: '/etc/ssl/certs'
+
+``ca_cert_dir`` can optionally point to a directory containing the CA certificates that you trust. Most linux distributions provide CA certificates via a package called ``ca-certificates``.
+If omitted, the default system CA used by Python is used.