Add Gruntfile Expose Test

Gruntfile can include secrets or other information that helps find
further vulnerabilities.

exposures/configs/gruntfile.yaml

@@ -0,0 +1,27 @@
+id: gruntfile
+
+info:
+  name: gruntfile exposure
+  author: sbani
+  severity: info
+  reference: https://gruntjs.com/sample-gruntfile
+  tags: config,exposure
+
+requests:
+  - method: GET
+    redirects: true
+    max-redirects: 3
+    path:
+      - "{{BaseURL}}/Gruntfile.js"
+      - "{{BaseURL}}/Gruntfile.coffee"
+
+    matchers-condition: and
+    matchers:
+      - type: word
+        words:
+          - "module.exports"
+        part: body
+
+      - type: status
+        status:
+          - 200