templates: fix typo "custm" -> "custom"
<li>
ALT + Click the Tailscale icon in the menu and hover over the Debug menu
</li>
- <li>Under "Custm Login Server", select "Add Account..."</li>
+ <li>Under "Custom Login Server", select "Add Account..."</li>
<li>
Enter "{{.URL}}" of the headscale instance and press "Add Account"
</li>
