Add warning for only ignore label. Fail on missing labels

Author: OptimumCode

Dangerfile.df.kts

@@ -4,8 +4,14 @@ import systems.danger.kotlin.*
 
 danger(args) {
   onGitHub {
-    if (issue.labels.isEmpty()) {
-      warn("PR must have labels")
+    val prLabels = issue.labels
+    when (prLabels.size) {
+      0 -> fail("PR must have labels")
+      1 ->
+        prLabels.find { it.name.equals("ignore", ignoreCase = true) }?.let {
+          warn("PR must have labels other than 'ignore'")
+        }
+      else -> {}
     }
   }
 }