mitmproxy : add the variable "SSLKEYLOGFILE" (#10306)

* mitmproxy : add the variable "SSLKEYLOGFILE"
source : https://docs.mitmproxy.org/stable/howto-wireshark-tls/

* mitmproxy : add ':' at the end of the description

* Update pages/common/mitmproxy.md

Co-authored-by: Lena <126529524+acuteenvy@users.noreply.github.com>

---------

Co-authored-by: Lena <126529524+acuteenvy@users.noreply.github.com>

pages/common/mitmproxy.md

@@ -15,3 +15,7 @@
 - Start `mitmproxy` using a script to process traffic:
 
 `mitmproxy --scripts {{path/to/script.py}}`
+
+- Export the logs with SSL/TLS master keys to external programs (wireshark, etc.):
+
+`SSLKEYLOGFILE="{{path/to/file}}" mitmproxy`