Added demo script for Slack utility package

demos/slack_util_pkg_demo.sql

@@ -0,0 +1,16 @@
+
+-- send message to Slack using webhook
+-- see https://api.slack.com/incoming-webhooks
+
+begin 
+  -- create your own incoming webhook in Slack, then paste the path to the webhook here
+  slack_util_pkg.set_webhook_path ('/services/T00000000/B00000000/XXXXXXXXXXXXXXXXXXXXXXXX');
+  -- send a basic message
+  slack_util_pkg.send_message ('Hello Slack World!');
+  -- send a formatted message
+  slack_util_pkg.send_message ('Hello *Slack* World! This is a _message from PL/SQL_ sent using the <https://github.com/mortenbra|Alexandria PL/SQL Utility Library>.');
+end;
+/
+
+
+