Add E2E test which installs extension

[melink14]

In order to catch problems like missing content scripts loading the extension in the browser would be good.

• Pack extension as CRX (Stackoverflow)
• Use browserstack to create remote browser with extension installed. (docs)
• Check for errors
• Added programmatic way to enable extension (Workaround)

Types of errors:

• Missing context script listed in manifest
• Turning on extension works. (test hover once?)
• Options page doesn't load or has errors; (click one box?)
• Background page has no errors.

[melink14]

https://github.com/thom4parisot/crx is a NPM module for packing CRX and is up to date.

[melink14]

I shouldn't need private key if I don't care about the extension ID.

[melink14]

chrome.exe's pack ability has some custom functionality (for example skipping dot files) so we may want to use that for increased coverage of problem types.