Post message for end of support (#268)

Author: hvaghani221

README.md

@@ -1,3 +1,7 @@
+# End of Support
+
+**Important:** The fluent-plugin-splunk-hec will reach End of Support on January 1, 2024. After that date, this repository will no longer receive updates from Splunk and will no longer be supported by Splunk. Until then, only critical security fixes and bug fixes will be provided.
+
 # fluent-plugin-splunk-hec
 
 [Fluentd](https://fluentd.org/) output plugin to send events and metrics to [Splunk](https://www.splunk.com) in 2 modes:<br/>