Set up library to allow importing from @app / @frogpond in a monorepo

[hawkrives]

There are no real changes to the code base here.

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So! This is part of a refurbished, repolished #1537 (the giant reorganization PR). That one tried to do three separate things (move components/ to the top level, reorganize app initialization, and restructure the app views); I've decided to break the changes into smaller chunks for review 😸

This PR sets up the infrastructure to allow us to do import * as c from '@app/components/colors' instead of import * as c from '../../../../../components/colors', in both Flow and Babel.

Code movements are coming up next.

Timeline

• Move components to source/
• Rename flux/ to redux/
• Reorganize app initialization
• Set up things to we can do import … from '@app/components/colors' instead of import … from '../../../../components/colors'
• Extract reusable views from views/ into modules/
• Automate-ish the loading of views from views/ and deprecate the views.js object