Add loader.js to the list of background scripts

[saagarjha]

What I Changed

I added loader.js to the list of background scripts, because it looks like analytics.js requires it. (Disclaimer: I am not a web developer, nor a user of this extension, so it's entirely possible I misunderstood the code–please do let me know if this isn't what you expected.)

Screenshots of Changes

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Issues Closed By This Pull Request

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