chore: enable system js build

[Caele]

Updates the Nebula dependency and enables the systemJS build artifact.

[Caele]

Had to leave nebula/cli-build at 3.0.3 due to an update to @rollup/plugin-node-resolve v14 which somehow breaks the table in particular.
The Nebula PR is this: qlik-oss/nebula.js#946
The change in @rollup/plugin-node-resolve is rollup/plugins#1245
I have yet to determine what actually happens and how to resolve it.

The actual error:

---> BUILDING SUPERNOVA
No name was provided for external module “stream” in “output.globals” – guessing “require$$7$1”.
Creating a browser bundle that depends on Node.js built-in modules (“stream”). You might need to include https://github.com/FredKSchott/rollup-plugin-polyfill-node