fix: pubdev/.snyk & pubdev/package.json to reduce vulnerabilities

The following vulnerabilities are fixed with a Snyk patch:
- https://snyk.io/vuln/npm:tunnel-agent:20170305

pubdev/.snyk

@@ -0,0 +1,8 @@
+# Snyk (https://snyk.io) policy file, patches or ignores known vulnerabilities.
+version: v1.12.0
+ignore: {}
+# patches apply the minimum changes required to fix a vulnerability
+patch:
+  'npm:tunnel-agent:20170305':
+    - gulp-sass > node-sass > request > tunnel-agent:
+        patched: '2018-06-26T00:24:09.178Z'

pubdev/package.json

@@ -4,7 +4,9 @@
   "description": "",
   "main": "gulpfile.js",
   "scripts": {
-    "lint:js": "eslint -o /tmp/lint.log --fix ./**/*.jsx"
+    "lint:js": "eslint -o /tmp/lint.log --fix ./**/*.jsx",
+    "snyk-protect": "snyk protect",
+    "prepare": "npm run snyk-protect"
   },
   "author": "",
   "license": "ISC",
@@ -77,6 +79,8 @@
     "semantic-ui-react": "^0.67.2",
     "through": "^2.3.8",
     "vinyl-source-stream": "^1.1.0",
-    "warning": "^3.0.0"
-  }
+    "warning": "^3.0.0",
+    "snyk": "^1.85.0"
+  },
+  "snyk": true
 }