This commit introduces a new search behind a release toggle (`typesense-search`). The search is based on [Typesense](http://typesense.org) and uses [Instantsearch.js](https://github.com/algolia/instantsearch) and the [Typesense Instantsearch adapter](https://github.com/typesense/typesense-instantsearch-adapter) for the UI components and logic.

The UI styling is not yet done, subsequent MRs will address this.