fix the extra_javascript include in base.html

[brunoruas2]

I was trying to use an additional js file according to the mkdocs documentation by passing the paths of the js files in the "extra_javascript" tag in mkdocs.yml, but it wasn't working.

When analyzing the code of the base.html file, I noticed that the import part of these files was missing. So I added it to the fork I made, and it worked for me.

            {%- for path in extra_javascript %}
                <script src="{{ path }}"></script>
            {%- endfor %}

[FernandoCelmer]