Move index.js to web_src and use webpack to pack them (#8598)

* Move index.js to web_src and use webpack

* Fix initHeatMap

* update eslint and move webpack to devDependencies

* update index.js

* add eslint env node

Makefile

@@ -434,7 +434,8 @@ npm-update: npm-check
 
 .PHONY: js
 js: npm
-	npx eslint public/js
+	npx eslint web_src/js webpack.config.js
+	npx webpack
 
 .PHONY: css
 css: npm