chore: Standardize build process

[paulbellamy]

What problem does your feature solve?

Right now we have both a Makefile (for rust) and a package.json (for JS). The distinction is unclear and means the build is spread across two tools.

What would you like to see?

We should standardize onto JS if possible, as that will be more familiar for the target frontend-dev audience. Maybe gulp (or another tool) could help here? I'm not sure what the latest from the next.js build-pipeline tooling is.

What alternatives are there?

Standardize onto makefiles, but that will not really fit with the next.js approach (and we would still need a package.json).