Javascript link in footer

[BackSeat]

I have a link that uses some javascript to display a popup form. I'd like this link to appear in the footer of every page. How can I do that? Here's an example of the link:

<a class="xxxx" href="javascript:void(0)" onclick="ml('show', 'zzzz', true)">link text</a>

[BackSeat]

In case anyone else wants to do this, I did it by editing config/_default/menus.en.toml and adding this:

[[footer]]
    title = ""
    name = "<a class=\"xxxx\" href=\"javascript:void(0)\" onclick=\"ml('show', 'zzzz', true)\">link text</a>"