jPicker function to class (used with `new`)
- Linting (ESLint): Add `valid-jsdoc` rule and make fixes; but turn off for
now due to <https://github.com/eslint/eslint/issues/11036> and
<https://github.com/eslint/eslint/issues/11037>
- Docs (JSDoc): Add some Markdown for variables, line breaks; tighten checks
for overly generic types (though allow for `.Function` as in
`jQuery.Function`) and avoid one previously missed instance