- The current make -j parallelization doesn't kill the remaining process
when one of them errors out, the causes confusion if let's css/js is not
building.

- This PR also refractors the help target to use comment based generator
which is more maintainable.

- Update the node scripts to not require `collectstatic` during
development, the runserver -> static server can find all the all files
from packages and serve them on demand.
- `make serve` now also installs python & node packages and builds the
static_src if they are outdated.

---------

Co-authored-by: Fredrik Jonsson <frjo@xdeb.org>