Update JavaScript dependencies

[danyeaw]

Fixes #324 by updating JS development dependencies:

• Updates po2json to a 1.0 beta version which removes dependencies on nomnom and replaces it with commander
• Updates less from version 2 to the latest less version
• Commander, gettext-parser, and gettext-to-messageformat were added as explicit dev dependencies because otherwise I was getting errors with unmet peer dependencies.
• Remove a dev dependency on bower
• Fix an issue where runtime dependency on google-caja was sometimes not pulling the right tagged version from GitHub by directly using the archive of the version
• Upgrade NodeJS on CI to version 16.x since some of the updated modules were incompatible with NodeJS 12 and 14.

Prior to the changes:

~/P/nbclassic (main|✔) $ yarn audit                                                                                     (nbclassic) 
yarn audit v1.22.22
22 vulnerabilities found - Packages audited: 721
Severity: 12 Moderate | 9 High | 1 Critical

Result after the change:

~/P/nbclassic (update-dependencies|✔) $ yarn audit                                                                      (nbclassic) 
yarn audit v1.22.22
┌───────────────┬──────────────────────────────────────────────────────────────┐
│ moderate      │ Bootstrap Cross-Site Scripting (XSS) vulnerability           │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Package       │ bootstrap                                                    │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Patched in    │ No patch available                                           │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Dependency of │ @bower_components/bootstrap-tour                             │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ Path          │ @bower_components/bootstrap-tour > bootstrap                 │
├───────────────┼──────────────────────────────────────────────────────────────┤
│ More info     │ https://www.npmjs.com/advisories/1102099                     │
└───────────────┴──────────────────────────────────────────────────────────────┘
1 vulnerabilities found - Packages audited: 420
Severity: 1 Moderate