Introduce OpenAPI specs (#4351)

* wip

* wip

* wip

* Update index.ts

* Update gen-openapi-spec.ts

* Update api.ja-JP.md

* Fix

* Improve doc

* Update gen-openapi-spec.ts

* Update redoc.html

* Improve doc

* Update gen-openapi-spec.ts

* Improve doc

* Update CHANGELOG.md

src/server/api/endpoints/admin/drive/files.ts

@@ -4,6 +4,8 @@ import define from '../../../define';
 import { fallback } from '../../../../../prelude/symbol';
 
 export const meta = {
+	tags: ['admin'],
+
 	requireCredential: false,
 	requireModerator: true,