Update JSDoc dependency to 3.4.0

[notmessenger]

Once jsdoc/jsdoc#996 is accepted the notmessenger/jsdoc dependency can be replaced with the "real" JSDoc

[notmessenger]

jsdoc/jsdoc#996 is no longer the issue. That issue was closed due to the problem reported in it being fixed by a separate PR. The problem now is that v3.3.3 of JSDoc, which includes the fix reported by jsdoc/jsdoc#996, complains about the use of export in files in the /app folder.

JSDoc 3.4.0 is slated to support ES2015 syntax - jsdoc/jsdoc#555 (comment)