feat: add Insights event sampling (#159)

See honeybadger-io/honeybadger-php#227

Author: stympy

config/honeybadger.php

@@ -160,6 +160,11 @@
          */
         'dispatch_interval_seconds' => BulkEventDispatcher::DISPATCH_INTERVAL_SECONDS,
 
+        /**
+         * The percentage of events to send
+         */
+        'sample_rate' => 100,
+
         /**
          * Events which should automatically be sent to Honeybadger Insights.
          * Note that to track redis events, you need to call `Redis::enableEvents()` in your app.