- Refactoring: Avoid unnecessary addEventListener false; change internal

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

editor/extensions/ext-xdomain-messaging.js

@@ -40,7 +40,7 @@ export default {
           message.error = err.message;
         }
         e.source.postMessage(JSON.stringify(message), '*');
-      }, false);
+      });
     } catch (err) {
       console.log('Error with xdomain message listener: ' + err);
     }