Add Gesso (#812)

Author: wadakatu

src/content/tools/gesso.md

@@ -0,0 +1,15 @@
+---
+name: Gesso
+description: Framework-agnostic OpenAPI contract testing for PHPUnit that validates requests and responses against your OpenAPI description and reports which endpoints, statuses, and content types your tests actually cover. Ships Laravel, Symfony, Pest, and PSR-7 adapters.
+categories:
+  - testing
+link: https://studio-design.github.io/gesso/
+languages:
+  php: true
+repo: https://github.com/studio-design/gesso
+oasVersions:
+  v2: false
+  v3: true
+  v3_1: true
+  v3_2: true
+---