Add a basic search page

[radostin04]

This implements #2

I've added a basic search page that fetches and displays search results from Algolia. I've also implemented the beginnings of a horziontal layout for AppCard, intended to emulate the horizontal watchapps result page from the legacy appstore.

I would need more information to solve the following problems:

• Screenshots do not currently display, as the screenshot format returns in the app info objects by Algolia is different from the one that AppCard expects. I assume this is intentional and that I should implement handling regardless, but I'd like to confirm beforehand
• Watchapps do not provide a list_image, only screenshots - the legacy appstore also only displayed screenshots for watchapps, but I think this is a bit weird - if the main appstore page displays icons, so should the search. Of course, to make this possible, list_image would need to be added to the Algolia search results - otherwise, I can replicate the legacy behavior of showing a screenshot
• I've hardcoded the URL and API key at this time - Is there a centralized place where URLs and configurations and such are stored? I couldn't find one.
• Pagination isn't implemented at this time - how many results should there be per page? The legacy appstore appears to use 39 for watchfaces and 15 for apps.

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