Add Sonic as search engines

Fast, lightweight & schema-less search backend. An alternative to Elasticsearch that runs on a few MBs of RAM.

README.md

@@ -1704,6 +1704,7 @@ A [search engine](https://en.wikipedia.org/wiki/Search_engine_(computing)) is an
 - [OpenSearch](https://opensearch.org) - Open source distributed and RESTful search engine. ([Source Code](https://github.com/opensearch-project/OpenSearch)) `Apache-2.0` `Java`
 - [Searx](https://searx.github.io/searx/) - Privacy-respecting, hackable metasearch engine. ([Demo](https://searx.space/), [Source Code](https://github.com/searx/searx)) `AGPL-3.0` `Python`
 - [sist2](https://github.com/simon987/sist2) - Lightning-fast file system indexer and search tool. ([Demo](https://sist2.simon987.net/)) `GPL-3.0` `C`
+- [sonic](https://github.com/valeriansaliou/sonic) - Sonic is a fast, lightweight and schema-less search backend. It ingests search texts and identifier tuples that can then be queried against in a microsecond's time. `MPL-2.0 license` `rust`
 - [Typesense](https://typesense.org) - Blazing fast, typo-tolerant open source search engine optimized for developer happiness and ease of use. ([Source Code](https://github.com/typesense/typesense)) `GPL-3.0` `C++`
 - [Whoogle](https://github.com/benbusby/whoogle-search) `⚠` - A self-hosted, ad-free, privacy-respecting metasearch engine. `MIT` `Python`
 - [Yacy](https://yacy.net/en/index.html) - Peer based, decentralized search engine server. ([Source Code](https://github.com/yacy/yacy_search_server)) `GPL-2.0` `Java`