add pre-commit package

package-lock.json

@@ -6535,6 +6535,28 @@
         }
       }
     },
+    "pre-commit": {
+      "version": "1.2.2",
+      "resolved": "https://registry.npmjs.org/pre-commit/-/pre-commit-1.2.2.tgz",
+      "integrity": "sha1-287g7p3nI15X95xW186UZBpp7sY=",
+      "dev": true,
+      "requires": {
+        "cross-spawn": "5.1.0",
+        "spawn-sync": "1.0.15",
+        "which": "1.2.14"
+      },
+      "dependencies": {
+        "which": {
+          "version": "1.2.14",
+          "resolved": "https://registry.npmjs.org/which/-/which-1.2.14.tgz",
+          "integrity": "sha1-mofEN48D6CfOyvGs31bHNsAcFOU=",
+          "dev": true,
+          "requires": {
+            "isexe": "2.0.0"
+          }
+        }
+      }
+    },
     "prelude-ls": {
       "version": "1.1.2",
       "resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.1.2.tgz",

package.json

@@ -41,6 +41,7 @@
         "geckodriver": "^1.9.0",
         "gulp": "^3.9.1",
         "mocha": "^4.0.1",
+        "pre-commit": "^1.2.2",
         "selenium-webdriver": "^3.6.0",
         "web-ext": "^2.2.2"
     }