Optimize performance for v3

Starting an issue here to keep track of the performance optimizations that can be done in v3:

[x] Use HTTP/2
[ ] Set proper cache-control headers for static assets. Consider using immutable
[ ] Set proper cache-control headers for API response. It can be a few days (or even a week) when module data has stabilized (e.g. Week 3 onwards)
[x] Code splitting for lazy loading (http://webpack.github.io/docs/code-splitting.html)
[x] Investigate using React Loadable or async loading of components
[ ] On initialization, fetch data for N modules at once in one request instead of making N requests. This will be enabled by GraphQL
[ ] Server-side search for module finder page (can be cached on client side once data is fully loaded and switch to client side filtering which can be used offline). This will be enabled by GraphQL
[ ] Brotli compression for Chrome and Firefox?
[x] Service workers to cache assets in supported browsers
[x] Investigate using Prepack
[ ] https://github.com/nolanlawson/optimize-js
[x] Consider using <link rel="preload"> for faster initial JSON loading - https://developer.mozilla.org/en-US/docs/Web/HTML/Preloading_content

References:

nusmodifications / nusmods