Implement tests for CreateOrJoinNH component

[pospi]

Following on from #12.

This will require working through use of @storybook/test-runner and @storybook/testing-library utility functions: https://storybook.js.org/blog/interaction-testing-with-storybook/

• Assert that it dispatches a create-nh event when the appropriate button is clicked
• Assert that it dispatches a join-nh event when the appropriate button is clicked and sends the CA pubKey in the expected event payload format

[pospi]

@weswalla I went ahead and started implementing this in #17 as well- I figure the two should be in the same PR.

Selection and interaction handling seems to be working, but there is some issue with the Jest mocks and event listeners which is preventing the assertions from working as expected. There may also be a bug with the create-nh event since it's currently not set to bubbling or composed, but you know better than me whether that is intentional.

Would you mind taking over? I think it's close. FYI I added some links to the various testing libraries' documentation in the developer docs since they aren't very well organised.

[weswalla]

@pospi I'm looking into this now

[pospi]

☹️ storybookjs/test-runner#336