Add slick slider in Docs

[thclark]

We could add a slick slider to the docs, allowing multiple images to be displayed in the banner.

To do this we can adapt the sphinx hello world tutorial...

In docs/source/_ext/slickslider.py :

from docutils import nodes
from docutils.parsers.rst import Directive


class SlickSlider(Directive):

    def run(self):
        paragraph_node = nodes.paragraph(text='Slick Slider!')
        return [paragraph_node]


def setup(app):
    app.add_directive("slickslider", SlickSlider)

    return {
        'version': '0.1',
        'parallel_read_safe': True,
        'parallel_write_safe': True,
    }

Line 18 of docs/source/conf.py might look like:

# If extensions (or modules to document with autodoc) are in another directory,
# add these directories to sys.path here. If the directory is relative to the
# documentation root, use os.path.abspath to make it absolute, like shown here.
#sys.path.insert(0, os.path.abspath('.'))
sys.path.append(os.path.abspath("./_ext"))

Line 34 of conf.py might look like:

    'sphinx_tabs.tabs',
    'sphinx.ext.mathjax',
    'sphinx.ext.ifconfig',
    'slickslider',
    'breathe',
    'exhale'
]

And index.rst might look like:

EnvironmentSTUDIO flow (**es-flow** for short) is a library for analysing and modeling atmospheric and marine boundary layers.

.. slickslider::