ENH: Include option to specify landing page / 404 custom html assets for html builder

[mmcky]

It would be nice to have the ability to specify path to html static assets you may want to use when constructing the site, such as a more sophisticated frontpage (index.html) and a 404.html etc.

jupyter_html_index = "path"
jupyter_html_404 = "path"

[mmcky]

this is currently supported as a theme support

If you place files in theme/html then they will be copied over to the website build directory _build/website/jupyter_html

https://github.com/QuantEcon/sphinxcontrib-jupyter/blob/master/sphinxcontrib/jupyter/writers/make_site.py

• [ ] we need to make theme path an option so that the paths aren't hard coded.

jupyter_html_theme = "theme/datascience"

which will then contain html, static, css etc.

[mmcky]

Will implement the following options

jupyter_theme = 'name'
jupyter_theme_path = <path>

jupyter_template_path = <path>
jupyter_template_html = <filename>
jupyter_template_pdf = <filename

this will support custom locations for theme or templates

[mmcky]

Closed with #233