Update README.md

Author: azurit

README.md

@@ -34,4 +34,5 @@ maps the regular CRS IDs from 900K for each rule to the range 9,900,000 - 9,999,
 | iredadmin-rule-exclusions-plugin    | 9,521,000 - 9,521,999 | [EsadCetiner/iredadmin-rule-exclusions-plugin](https://github.com/EsadCetiner/iredadmin-rule-exclusions-plugin)         | 3rd party | ✅ tested | ![Integration tests](https://github.com/EsadCetiner/iredadmin-rule-exclusions-plugin/actions/workflows/integration.yml/badge.svg) |
 | wordpress-hardening-plugin          | 9,522,000 - 9,522,999 | [eilandert/wordpress-hardening-plugin](https://github.com/eilandert/wordpress-hardening-plugin)                         | 3rd party | untested            |      |
 | database-logging-plugin             | 9,523,000 - 9,523,999 | [coreruleset/database-logging-plugin](https://github.com/coreruleset/database-logging-plugin)                           | official  | untested            |      |
+| referer-hardening-plugin            | 9,524,000 - 9,524,999 | [coreruleset/referer-hardening-plugin](https://github.com/coreruleset/referer-hardening-plugin)                         | official  | untested            |      |
 | incubator                           | 9,900,000 - 9,999,999 | [coreruleset/incubator-plugin](https://github.com/coreruleset/incubator-plugin)                                         | official  | -                   |      |