testing: Add frontend tests. #52
Description
Currently, we test the code examples in a node runtime. However, zulip-js also functions in the browser, and we should add bundling and testing in a browser based environment as well.
This task is open ended in terms of which bundler(s) to use and which testing framework to use. Ideally, we should be able to have a way to run all the currently existing tests in a stubbed out environment without the node utilities/packages available.
For reference: #47