Run npm test as a pre-commit hook

Adds the `pre-commit` npm package which automatically
handles git pre-commit hooks via package.json and runs
`npm run test` by default.

https://www.npmjs.com/package/pre-commit

Requires an `npm install`

Change-Id: Ia5950242bced753c42fc804fd686bc239c335aa3

package-lock.json

@@ -2440,6 +2440,12 @@
 				"lcid": "1.0.0"
 			}
 		},
+		"os-shim": {
+			"version": "0.1.3",
+			"resolved": "https://registry.npmjs.org/os-shim/-/os-shim-0.1.3.tgz",
+			"integrity": "sha1-a2LDeRz3kJ6jXtRuF2WLtBfLORc=",
+			"dev": true
+		},
 		"os-tmpdir": {
 			"version": "1.0.2",
 			"resolved": "https://registry.npmjs.org/os-tmpdir/-/os-tmpdir-1.0.2.tgz",
@@ -2647,6 +2653,17 @@
 			"integrity": "sha1-h/OPnxj3dKSrTIojL1xc6IcqnRU=",
 			"dev": true
 		},
+		"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"
+			}
+		},
 		"prelude-ls": {
 			"version": "1.1.2",
 			"resolved": "https://registry.npmjs.org/prelude-ls/-/prelude-ls-1.1.2.tgz",
@@ -2980,6 +2997,16 @@
 			"resolved": "https://registry.npmjs.org/source-map/-/source-map-0.5.7.tgz",
 			"integrity": "sha1-igOdLRAh0i0eoUyA2OpGi6LvP8w="
 		},
+		"spawn-sync": {
+			"version": "1.0.15",
+			"resolved": "https://registry.npmjs.org/spawn-sync/-/spawn-sync-1.0.15.tgz",
+			"integrity": "sha1-sAeZVX63+wyDdsKdROih6mfldHY=",
+			"dev": true,
+			"requires": {
+				"concat-stream": "1.6.0",
+				"os-shim": "0.1.3"
+			}
+		},
 		"spdx-correct": {
 			"version": "1.0.2",
 			"resolved": "https://registry.npmjs.org/spdx-correct/-/spdx-correct-1.0.2.tgz",

package.json

@@ -17,6 +17,7 @@
 		"grunt-jsonlint": "1.1.0",
 		"grunt-notify": "0.4.5",
 		"grunt-stylelint": "0.8.0",
+		"pre-commit": "1.2.2",
 		"stylelint": "7.8.0",
 		"stylelint-config-wikimedia": "0.4.1"
 	}