Have a concept for optional frontend libraries

[xi]

Some frontend libraries are only used on specific pages (e.g. leaflet for maps). Sometimes we just include these libraries in the webpack bundle so that it gets quite big (~1.5MB at the moment). Sometimes we only load them on the pages where they are needed, which adds complexity.

We should find a consistent solution for this which balances performance and code complexity.

[xi]

For reference, this are the mechanisms currently in use:

• webpack
• django form assets
• an "extra_js" template block