CI: add checks for Python and npm package licenses

[flodolo]

A few notes:

1. I originally wanted to use licensecheck, because you don't need to install the dependencies with that tool. Unfortunately I can't seem to make it check other requirements files (filed issue here).
2. For npm, license-checker hasn't been updated in a while, there's a fork. One general issue is that --failOn will print nothing when it fails (i.e. there is a GPL package), but if it doesn't fail it prints again the same output as license-checker. Opted to print a summary on the 2nd run.
3. Given you need to install the dependencies for both, I opted to have the check as a step in existing workflows (originally I had them in a new separate workflow), and to install the 2 packages directly in the workflow.

[flodolo]

Modern development…

Npm 842 packages

├─ MIT: 705
├─ ISC: 42
├─ BSD-2-Clause: 28
├─ BSD-3-Clause: 27
├─ Apache-2.0: 25
├─ (MIT OR CC0-1.0): 3
├─ 0BSD: 2
├─ BSD: 2
├─ (Unlicense OR Apache-2.0): 1
├─ Python-2.0: 1
├─ CC-BY-4.0: 1
├─ (Apache-2.0 OR MPL-1.1): 1
├─ Custom: : 1
├─ Custom: https://www.highcharts.com/license: 1
├─ UNLICENSED: 1
└─ CC0-1.0: 1

Python only 108 packages.