feat: serve static assets through CDN

[chriscasto]

Both the public and partner sites contain static assets (images, etc) and generate additional static files (JS, CSS, HTML) during the build process. This static content should be served from a CDN rather than directly from the application instances. There are two ways to do this:

1. Copy static assets over to an S3 bucket during build time
2. Put a CDN in front of the application instances and cache requests on certain paths

The first option requires more changes, but makes it easier to keep a clean separation between static and dynamic content. The latter is easier, but requires making changes that could temporarily disrupt access to the sites while deployment is in progress.