docs: how to create the proper CA (#5370)

Co-authored-by: Maximilian Hils <git@maximilianhils.com>

CHANGELOG.md

@@ -9,6 +9,8 @@
 
 * Fix multipart form content view being unusable.
   ([#6653](https://github.com/mitmproxy/mitmproxy/pull/6653), @DaniElectra)
+* Documentation Improvements on CA Certificate Generation
+  ([#5370](https://github.com/mitmproxy/mitmproxy/pull/5370), @zioalex)  
 
 ## 07 March 2024: mitmproxy 10.2.4
 

docs/src/content/concepts-certificates.md

@@ -191,6 +191,12 @@ use it to generate certificates:
         X509v3 Basic Constraints: critical
             CA:TRUE
 
+For example, when using OpenSSL, you can create a CA authority as follows:
+
+```shell
+openssl req -x509 -new -nodes -key ca.key -sha256 -out ca.crt -addext keyUsage=critical,keyCertSign
+cat ca.key ca.crt > mitmproxy-ca.pem
+```
 
 ## Using a client side certificate