add WPT tests

Author: zbjornson

package.json

@@ -29,6 +29,8 @@
     "test": "mocha test/*.test.js",
     "pretest-server": "node-gyp build",
     "test-server": "node test/server.js",
+    "generate-wpt": "node ./test/wpt/generate.js",
+    "test-wpt": "mocha test/wpt/generated/*.js",
     "install": "node-pre-gyp install --fallback-to-build --update-binary",
     "dtslint": "dtslint types"
   },
@@ -57,6 +59,7 @@
     "assert-rejects": "^1.0.0",
     "dtslint": "^4.0.7",
     "express": "^4.16.3",
+    "js-yaml": "^4.1.0",
     "mocha": "^5.2.0",
     "pixelmatch": "^4.0.2",
     "standard": "^12.0.1",