This commit transitions landing-page.css from the Django pipeline
to being compiled by webpack as landing-page.scss under the
'landing-page' and 'integration' bundles.
Apparently, essentially every one of our landing pages extending
portico.html had two copies of portico.css included in their head
section; one from porticocustomhead (or the super of customhead) and
the other directly included.
Clean this up by removing all these duplicate inclusions of the
portico stylesheet.
Apparently, the filters implementation was doing some sort of strange
caching, where you would need to restart the server in order to
refresh for changes to the markdown content.
We fix this by switching to just calling the render_markdown_path
function from Jinja2.
Fixes#5974.
Akash Nimare
Rishi Gupta
Tim Abbott
Max Nussenbaum
Armaan Ahluwalia
Vishnu Ks
Brock Whittaker