Fix GITHUB_WEBHOOK_TOKEN env var example (#89)

As in https://github.com/cpanato/github_actions_exporter/blob/7b83bec7d90a7b037b3f7f14fff7e743ba96c3c9/main.go#L25

Signed-off-by: Laurenz <[email protected]>

Author: lalten

README.md

@@ -73,7 +73,7 @@ make test
 
 ```bash
 cd example/
-export WEBHOOK_SECRET="..."
+export GITHUB_WEBHOOK_TOKEN="..."
 export GITHUB_TOKEN="..."
 export GITHUB_ORG="..."
 docker-compose up --build