This matters for user security.
I didn't touch blog posts & pages related to past conferences.
The `content/docs` could be HTTPS-ified as well but it contains lots of HTTP
links so maybe that'd be best done in a separate PR.
logo-large was a custom version of the logo made just for the banner background. It was also scaled up manually rather than taking advantage of svg's inherit scaling. This change reduces its size, makes it just a plain white version of the react logo, and moves most of the custom stuff into css. It also moves it from the static folder, over to the icons folder where it can be imported as a url.
