chore: update opa plugin .env template

Signed-off-by: Frederico Araujo <[email protected]>

Author: araujof

plugins/external/opa/.env.template

@@ -21,3 +21,6 @@ PLUGINS_CONFIG=./resources/plugins/config.yaml
 
 # Configuration path for chuck mcp runtime
 CHUK_MCP_CONFIG_PATH=./resources/runtime/config.yaml
+
+# Path to the repo policy file (optional, default: ./opaserver/rego/policy.rego)
+# POLICY_PATH=./opaserver/rego/policy.rego