[dev] Run npm t on Git pre-commit hook

Execute `npm test` prior to committing. This saves back-and-forth with
Jenkins. This is the same configuration used by Popups,
MobileFrontend, MinervaNeue, NearbyPages, ContentTranslation, and
others.

Change-Id: If61ab4f28b0ccd38492d11a4cd8a92a97b2eb582

package-lock.json

@@ -8606,6 +8606,12 @@
 			"integrity": "sha1-hUNzx/XCMVkU/Jv8a9gjj92h7Cc=",
 			"dev": true
 		},
+		"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",
@@ -9165,6 +9171,28 @@
 			"integrity": "sha512-N7h4pG+Nnu5BEIzyeaaIYWs0LI5XC40OrRh5L60z0QjFsqGWcHcbkBvpe1WYpcIS9yQ8sOi/vIPt1ejQCrMVrg==",
 			"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": "^5.0.1",
+				"spawn-sync": "^1.0.15",
+				"which": "1.2.x"
+			},
+			"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",
@@ -10861,6 +10889,16 @@
 			"integrity": "sha512-q/JSVd1Lptzhf5bkYm4ob4iWPjx0KiRe3sRFBNrVqbJkFaBm5vbbowy1mymoPNLRa52+oadOhJ+K49wsSeSjTA==",
 			"dev": true
 		},
+		"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": "^1.4.7",
+				"os-shim": "^0.1.2"
+			}
+		},
 		"spdx-correct": {
 			"version": "3.1.0",
 			"resolved": "https://registry.npmjs.org/spdx-correct/-/spdx-correct-3.1.0.tgz",

package.json

@@ -24,6 +24,7 @@
 		"less": "3.8.1",
 		"less-loader": "4.1.0",
 		"mustache": "3.0.1",
+		"pre-commit": "1.2.2",
 		"stylelint": "10.0.1",
 		"stylelint-config-wikimedia": "0.9.0",
 		"svgo": "1.3.2"