Storing it in an array is not a bad idea. You can create a separated data.js
file that contains all the array initializations and then just include it into a background page as a usual script.
Other possibility would be localStorage (but you need to initialize it somehow, which means probably reading from an array and saving to a storage, which makes localStorage kind of useless extra step). localStorage is more useful when you want to preserve user created data between extension upgrades.
WebDB would be an overkill here I think, plus you still need to initialize it somehow, which again means reading from an array. The only advantage is that you would be able to run data queries, but js implementation in Chrome has lots of array manipulation methods so you can emulate queries on arrays too.
I think in your case if all the data is defined upfront and never changes arrays would be the best solution.