fix: package.json, package-lock.json & .snyk to reduce vulnerabilities (#5271)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JS-PDFJSDIST-469200


The following vulnerabilities are fixed with a Snyk patch:
- https://snyk.io/vuln/SNYK-JS-HTTPSPROXYAGENT-469131

.snyk

@@ -0,0 +1,10 @@
+# Snyk (https://snyk.io) policy file, patches or ignores known vulnerabilities.
+version: v1.13.5
+ignore: {}
+# patches apply the minimum changes required to fix a vulnerability
+patch:
+  SNYK-JS-HTTPSPROXYAGENT-469131:
+    - '@alfresco/adf-cli > npm-registry-fetch > make-fetch-happen > https-proxy-agent':
+        patched: '2019-11-20T10:48:59.194Z'
+    - '@alfresco/js-api > @alfresco/adf-cli > npm-registry-fetch > make-fetch-happen > https-proxy-agent':
+        patched: '2019-11-20T10:48:59.194Z'

package.json

@@ -54,7 +54,9 @@
     "06s": "",
     "clean": "rimraf dist ./node_modules typings lib/dist",
     "clean-lock": "rimraf package-lock.json",
-    "lint:staged": "lint-staged"
+    "lint:staged": "lint-staged",
+    "snyk-protect": "snyk protect",
+    "prepare": "npm run snyk-protect"
   },
   "repository": {
     "type": "git",
@@ -112,14 +114,15 @@
     "moment-es6": "^1.0.0",
     "ng2-charts": "1.6.0",
     "ngx-monaco-editor": "7.0.0",
-    "pdfjs-dist": "2.0.489",
+    "pdfjs-dist": "2.0.943",
     "raphael": "2.2.7",
     "reflect-metadata": "0.1.13",
     "remark-validate-links": "^8.0.0",
     "rxjs": "^6.2.2",
     "systemjs": "0.19.27",
     "web-animations-js": "2.3.1",
-    "zone.js": "~0.8.26"
+    "zone.js": "~0.8.26",
+    "snyk": "^1.250.0"
   },
   "devDependencies": {
     "@angular-devkit/build-angular": "^0.13.4",
@@ -256,5 +259,6 @@
     "hooks": {
       "pre-commit": "npm run lint:staged"
     }
-  }
+  },
+  "snyk": true
 }