Add extra test

cmd/pint/tests/0138_annoation_regex_key_required.txt

@@ -0,0 +1,26 @@
+pint.error --no-color lint rules
+! stdout .
+cmp stderr stderr.txt
+
+-- stderr.txt --
+level=info msg="Loading configuration file" path=.pint.hcl
+rules/0001.yml:1-2 Bug: annotation_.* annotation is required (alerts/annotation)
+ 1 | - alert: Instance Is Down 1
+ 2 |   expr: up == 0
+
+level=info msg="Problems found" Bug=1
+level=fatal msg="Fatal error" error="found 1 problem(s) with severity Bug or higher"
+-- rules/0001.yml --
+- alert: Instance Is Down 1
+  expr: up == 0
+
+-- .pint.hcl --
+parser {
+  relaxed = [".*"]
+}
+rule {
+  annotation "annotation_.*" {
+    required = true
+    severity = "bug"
+  }
+}