Can't load index for sites with base_path

[MaxLap]

If your site has a base_path (in bridgetown.config.yml).

The fetch in

bridgetown-quick-search/frontend/javascript/index.js

Line 157 in 58f7223

const response = await fetch(`/bridgetown_quick_search/index.json`)

returns a 404 since it's missing that base_path.