A step towards a real solution for https://github.com/vector-im/riot-web/issues/7305
This approach makes use of `npm link` to remove the use of symlinks in the build process. The build process has also been altered to invoke the build process of each underlying SDK (react, js). This means that one can now `npm link` and `npm start` and have a working environment.
At the same time, parallelshell was dropped due to lack of maintenance from the maintainer.
As per https://github.com/vector-im/riot-web/issues/7083
The package-lock file is currently not bringing any of the benefits
it's supposed to bring because we don't do the neccessary things to
massage it during the release process. Remove it until we actually
manage it correctly.