js: Add jsdoc, update webpack-cli dependency

• package.json:
  • the old webpack-cli version depended on two packages with vulnerabilities, set to minimum version 3.0.8 to fix this (nodesecurity.io/advisories/157, nodesecurity.io/advisories/612)
  • added License identifier

• README: Updated documentation

• jsdoc.conf: Added a configuration file for jsdoc

• some minor documentation changes, indentations