v1.8: Negative keyword search

[gui machiavelli]

v1.8 allows users to exclude terms from search by prepending a - to search terms: "-escape room".

Tasks

• Update search API reference, around the same place where we describe phrase/placeholder search behavior

Reference

• engine issue: meilisearch/meilisearch#4422
• PRD: https://meilisearch.notion.site/API-usage-of-negative-operator-5279c6aaeaac4ab9a365cab273970f6b
• SME: @Kerollmops