Update Square connect type definitions (v20190508) + improvements (#36067)

* Add Square dev as a reviewer + add ApiClient, EmployeesApi and InventoryApi definitions

* Update Square connect type definitions (v20190508)

* Fix ENUM naming (to be as in swagger)

types/square-connect/README.md

@@ -0,0 +1,23 @@
+# Type definitions for square-connect
+
+This is an unofficial package of type definitions for [square-connect][1] which is _mostly_ generated automatically by [swagger-codegen][2]. 
+In case you are facing some issues - feel free to contribute or open an issue.
+
+# Installation
+
+`npm i @types/square-connect`
+> make sure that `square-connect` package is installed too
+
+# Contribution
+
+* Clone the [DefinitelyTyped][3] project
+    * or update if you already have it (`git fetch upstream && git reset --hard upstream/master`)
+* Add your changes and commit them (in case of error in [api.json][4] too, let the Square team know about it)
+* Test your changes:
+    * `npm run lint square-connect`
+    * `npm run test`
+
+[1]: https://docs.connect.squareup.com
+[2]: https://github.com/swagger-api/swagger-codegen
+[3]: https://github.com/DefinitelyTyped/DefinitelyTyped
+[4]: https://github.com/square/connect-api-specification/blob/master/api.json