Improve site performance on slow networks / mobile

[arimeq]

There is a number of optimisations that can be used here.

• start using Flask-Minify is probably the easiest thing that will already help
• avoid downloading code in runtime from CDNs; instead download a copy upon build and bundle everything together in order to reduce number of network requests
• enable data reload without restarting whole frontend
• configure service worker / PWA

[ttomasz]

Did you try to measure how much these steps would impact the load time?

With traditional websites minifying is great but here we have very little static resources while we load like 2MB of GeoJSON data so I'm not sure minifying 200KB of HTML, JS, CSS to 100KB will have a significant effect.

[ttomasz]

As for optimizing GeoJSON once it becomes too heavy we can switch to vector tiles