Spell out that one.one.one.one addition is for DoT

Author: RebeccaTamachiro

src/content/docs/1.1.1.1/setup/linux.mdx

@@ -49,6 +49,12 @@ sudo <EDITOR> /etc/systemd/resolved.conf
 
 2. In the editor, add or edit the following lines:
 
+```txt
+[Resolve]
+DNS=1.1.1.1
+```
+To use DNS over TLS, add `#one.one.one.one` as in the following example:
+
 ```txt
 [Resolve]
 DNS=1.1.1.1#one.one.one.one