Fixes tests and part of the CI pipeline

[StefanoCappellini]

This should fix #60

• Introduces the test-ci command for npm, removing the --watchAll options that caused the pipeline to hang
• Splits the test pipeline commands, thus they can be easily inspected
• Inside the test.yml, it performs the build before the test, because tests DEPEND ON the md-page artifact
• Adds workflow_dispatch for the test pipeline
• Updates the DEV_README

We should, however, discuss the point of the --watchAll if we are testing the build artifact. Should we test (at least on dev) the script itself directly, or should we discourage the --watchAll?

Let me know

[oscarmorrison]

Thanks @StefanoCappellini