Resolves #207 - Adding automated tests to CI

[alexcottner]

Resolves #207 - adding automated tests to CI pipeline.

This is adding selenium tests that we can run to have confidence in our changes before merging and/or running against a dev firefox branch.

ToDo:

• Add a couple more tests
• Integrate into github actions
• Clean up code (maybe add prettier?)
• Updated readme with notes on running automated tests

Notes:

• This works well with selenium-webdriver, although we have migrated away from that in some of our other projects
• Tried to do this with playwright at first, but extension testing for firefox appears unsupported at this time.
• Tried to do this with puppeteer by connecting to the web-ext browser as well, but it kept hanging. The dom loaded events seemed to not work quite right.
• Expecting some potentially large feedback from this one, so let it rip.

[leplatrem]

Can we wait for a certain selector instead?

[alexcottner]

The problem here is it marks the rows as busy/ready one at a time, so the waitForLoad call doesn't work reliably as it's a race condition. Maybe we could use DOMAttrModified events and give ourselves a debounce so we wait 200ms after the last busy is removed? 🤔

[alexcottner]

Switched to a debounce timeout that relies on a MutationObserver. It's kinda ugly. It has to inject an element to work because I don't see a way to pipe those events out of the browser (there appears to be a chrome option but no firefox option).

But, it seems to work perfectly. I tried to make the code as readable as possible.