Add TROUBLESHOOTING.md

Author: colto

TROUBLESHOOTING.md

@@ -0,0 +1,16 @@
+If you have a non-library SendGrid issue, please contact our [support team](https://support.sendgrid.com).
+
+If you can't find a solution below, please open an [issue](https://github.com/sendgrid/ruby-http-client/issues).
+
+## Table of Contents
+* [Viewing the Request Body](#request-body)
+
+## Viewing the Request Body
+
+When debugging or testing, it may be useful to exampine the raw request body to compare against the [documented format](https://sendgrid.com/docs/API_Reference/api_v3.html).
+
+You can do this right before you call: `response = response = client.version('v3').api_keys.post(request_body: request_body)` like so:
+
+```ruby
+puts request_body
+```