Enabled Mullvad DNS over HTTPS and added usage guide

how-to-configure-firefox-for-privacy-and-security/README.md

@@ -16,7 +16,7 @@ Listed: true
 
 - When copy/pasting commands that start with `$`, strip out `$` as this character is not part of the command
 
-## Guide
+## Setup guide
 
 ### Step 1: install [Firefox](https://www.mozilla.org/en-US/firefox/new/)
 
@@ -24,6 +24,8 @@ Go to [https://www.mozilla.org/en-US/firefox/new/](https://www.mozilla.org/en-US
 
 ### Step 2: add [user.js](./user.js) to profile
 
+> Heads-up: enables [Mullvad DNS over HTTPS](https://mullvad.net/en/help/dns-over-https-and-dns-over-tls/).
+
 > Heads-up: see [arkenfox/user.js](https://github.com/arkenfox/user.js/) to explore more settings.
 
 #### Start Firefox, paste “about:profiles” in address bar and press enter.
@@ -54,4 +56,32 @@ $ curl --fail --remote-name https://sunknudsen.com/static/media/privacy-guides/h
 
 ### Step 6: configure containers (see episode)
 
+### Step 7: check for DNS and WebRTC leaks
+
+Go to [https://mullvad.net/en/check](https://mullvad.net/en/check).
+
+![Connection check](connection-check.png)
+
+👍
+
+---
+
+## Usage guide
+
+### Temporarily disable cookie and site data deletion (useful when Firefox is restarted to install update or one wishes to reboot computer while persisting Firefox sessions)
+
+> Heads-up: “Delete cookies and site data when Firefox is closed” will be enabled again next time Firefox starts.
+
+Start Firefox, paste “about:preferences#privacy” in address bar and press enter.
+
+Disable “Delete cookies and site data when Firefox is closed”.
+
+👍
+
+---
+
+## Want things back the way they were before following this guide? No problem!
+
+### Delete `user.js` and set Firefox settings as they were before following guide.
+
 👍