Fix code block in README

     wget -q https://packages.mozilla.org/apt/repo-signing-key.gpg -O- | sudo tee /etc/apt/keyrings/packages.mozilla.org.asc > /dev/null
     echo "deb [signed-by=/etc/apt/keyrings/packages.mozilla.org.asc] https://packages.mozilla.org/apt mozilla main" | sudo tee -a /etc/apt/sources.list.d/mozilla.list > /dev/null
     echo '
-Package: *
-Pin: origin packages.mozilla.org
-Pin-Priority: 1000
-' | sudo tee /etc/apt/preferences.d/mozilla
+    Package: *
+    Pin: origin packages.mozilla.org
+    Pin-Priority: 1000
+    ' | sudo tee /etc/apt/preferences.d/mozilla
     sudo apt update
     sudo apt install firefox