[APPS-1544] Fire ready event from readified_js

:koala: :+1:

/cc @zendesk/quokka

### Description
To implement LB we added events to framework.js and installed.js. This PR fires the same event that installed.js would have if it was loaded from the server when `zat serve` is being used.

### References
 - Jira link: https://zendesk.atlassian.net/browse/APPS-1544

### Risks
  - If readified_js is ever called twice, it will fire the ready event twice which will likely break Lotus