Update README

README.md

@@ -1,3 +1,25 @@
 # Propaganda
 
 Announces merges in GitHub and GitLab to a slack incoming webhook.
+
+Propaganda, from the spanish meaning: advertisement
+
+> a notice or announcement in a public medium promoting a product, service, or event.
+
+## Usage
+
+```
+Usage of ./propaganda:
+  -address string
+    	listening address (default ":9092")
+  -config string
+    	configuration file to use (default "propaganda.yml")
+  -debug
+    	enable debug logging
+  -match-pattern string
+    	match string regex (default "\\[announce\\]")
+  -metrics string
+    	metrics path (default "/metrics")
+  -webhook-url string
+    	slack webhook url (default SLACK_WEBHOOK_URL env var)
+```