add npmignore file

.npmignore

@@ -0,0 +1,29 @@
+node_modules
+.DS_Store
+npm-debug.log
+.vscode
+
+lighthouse-extension/dist
+lighthouse-core/third_party/src
+**/pages/scripts/lighthouse-report.js
+coverage
+
+lighthouse-cli/results
+results
+results.html
+last-run-results.html
+
+*.trace.json
+*.screenshots.html
+*.report.html
+
+closure-error.log
+
+!lighthouse-cli/index.js
+lighthouse-cli/*.map
+
+lighthouse-cli/commands/*.map
+
+lighthouse-cli/types/*.js
+lighthouse-cli/types/*.map
+