Add a hook for custom CSS directions about pelican-themes

[rask004]

There is a way. A theme can have custom jinja2 variables and conditional code:

{% if CUSTOM_CSS %}
    <link rel="stylesheet" href="{{ SITEURL }}/{{ CUSTOM_CSS }}"}
{% endif %}

But the blog config will need to define this variable, and the EXTRA_PATH_METADATA as well to copy the file correctly into the blog file structure, e.g.:

EXTRA_PATH_METADATA = {
    'extras/custom.css':  {'path': 'custom.css'}
}

Do you need any further help with this, @nikipore ?

[nikipore]

Thanks @rask004.