fix: don't require recommend for brands plugin

[sbellone]

If you currently run the demo without Recommend, the popup doesn't display because the recommend index isn't found.

Since Recommend is complex to setup, I propose to not rely on it by default, so anyone can run the demo more easily.

This PR uses the same approach than #31 to fetch the most popular brand facets from the search results.
I'm also leaving the recommend code commented to give pointer about how to integrate Recommend.

Note: since our demo index is not fully trained, this approach actually works better:

• the current demo displays Lacy-D, Arlene and Lacy-S
• locally I now get Apple, Sony, Lacy-D and Garmin

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SFCC-389