Document differences between production and local development

### Describe the problem that you'd like solved

For new contributors, a short list of the differences between the production site and the local development environment might be good, so they can better tell if their local development environment is behaving correctly.

For example, certain links (e.g. `/about`) by default won't have content locally, and the carousels on the home page look different to the production environment. This can be confusing for new contributors.

### Proposal & Constraints

Perhaps a new page on the wiki with the differences could be created, and then it could be linked to from [Start the app](https://github.com/internetarchive/openlibrary/tree/master/docker#start-the-app) in the Docker documentation, and in [Logging in](https://github.com/internetarchive/openlibrary/wiki/Getting-Started#logging-in) in the Getting Started section of the Wiki.

### Stakeholders

@liaozhuzhu