Unable to set footer.html template

[Sdaher21]

I want to use my own footer.html template using sphinx-book-theme. I created it like this (not sure it's right) and then used the extra_footer in the html_theme_options:

For some reason, the output just says footer at the bottom and not the content of the .html file.

[choldgraf]

I'm adding footer support in #677 - I'll close this once that is merged!